JP4224089B2 - Imaging apparatus, defect inspection apparatus, defect inspection method, and electron beam inspection apparatus - Google Patents

Description

  The present invention relates to an inspection apparatus for inspecting defects or the like of a pattern formed on a surface to be inspected using an electron beam, and more specifically, inspecting an electron beam as in the case of detecting a wafer defect in a semiconductor manufacturing process. Inspection that irradiates the target and captures secondary electrons that change according to the surface properties to form image data, and inspects the pattern formed on the surface of the inspection target with high throughput based on the image data The present invention relates to an apparatus and a device manufacturing method for manufacturing a device with high yield using such an inspection apparatus. More specifically, the present invention relates to a detection apparatus using a projection method using a surface beam and a device manufacturing method using the apparatus.

  Moreover, in the semiconductor process, the design rule is about to reach the age of 100 nm, and the production form is shifting from small-quantity mass production represented by DRAM to high-variety small-quantity production such as SOC (Silicon on chip). . Along with this, the number of manufacturing processes increases, and it is essential to improve the yield for each process, and defect inspection due to the process becomes important. The present invention relates to an apparatus used for inspecting a wafer after each step in a semiconductor process, and relates to an inspection method and apparatus using an electron beam or a device manufacturing method using the same.

Background Art and Problems to be Solved by the Invention

  With the high integration of semiconductor devices and the miniaturization of patterns, inspection apparatuses with high resolution and high throughput are required. In order to investigate a defect of a wafer of one 100 nm design rule, a resolution of 100 nm or less is necessary, and an inspection amount increases due to an increase in manufacturing process due to high integration of devices, so that high throughput is required. . In addition, as the number of devices increases, the inspection apparatus is also required to have a function of detecting a contact failure (electrical defect) of a via that connects wirings between layers. Currently, optical defect inspection devices are mainly used. However, in terms of resolution and contact defect inspection, defect inspection devices that use electron beams instead of optical defect inspection devices will be used in the future. Expected to become mainstream. However, the electron beam type defect inspection apparatus has a weak point, which is inferior to the optical method in terms of throughput.

  Therefore, development of an inspection apparatus capable of detecting electric defects with high resolution and high throughput is required. The resolution in the optical system is said to be limited to 1/2 of the wavelength of light to be used, and is about 0.2 μm in the case of visible light that has been put into practical use.

  On the other hand, as a method using an electron beam, a normal scanning electron beam method (SEM method) has been put into practical use, with a resolution of 0.1 μm and an inspection time of 8 hours / sheet (20 cm wafer). The electron beam method is also characterized in that it is possible to inspect electric defects (disconnection of wiring, poor conduction, poor conduction of vias, etc.). However, the inspection time is very slow, and the development of a defect inspection apparatus with a high inspection speed is expected.

  In general, an inspection apparatus is expensive and has a lower throughput than other process apparatuses. Therefore, the inspection apparatus is currently used after an important process, for example, after etching, film formation, or CMP (chemical mechanical polishing) planarization. ing.

  A scanning (SEM) type inspection apparatus using an electron beam will be described. The SEM inspection apparatus narrows the electron beam (this beam diameter corresponds to the resolution), scans it, and irradiates the sample in a line shape. On the other hand, the observation region is irradiated with the electron beam in a planar shape by moving the stage in a direction perpendicular to the scanning direction of the electron beam. The scanning width of the electron beam is generally several 100 μm. A secondary electron from a sample generated by irradiation of the narrowed electron beam (referred to as a primary electron beam) is detected by a detector (scintillator + photomultiplier (photomultiplier)) or a semiconductor detector (PIN diode type). Etc.). The coordinates of the irradiation position and the amount of secondary electrons (signal intensity) are combined and imaged and stored in a storage device, or an image is output on a CRT (CRT). The above is the principle of SEM (scanning electron microscope), and a defect in a semiconductor (usually Si) wafer in the process is detected from an image obtained by this method. The inspection speed (corresponding to the throughput) is determined by the amount of primary electron beam (current value), the beam diameter, and the response speed of the detector. The beam diameter is 0.1 μm (which may be considered to be the same as the resolution), the current value is 100 nA, the detector response speed is 100 MHz, and the inspection speed is said to be about 8 hours per 20 cm diameter wafer in this case. ing. This inspection speed is very slow (1/20 or less) compared to the optical system, which is a major problem (defect).

  Moreover, as for the prior art of the inspection apparatus related to the present invention, an apparatus using a scanning electron microscope (SEM) has already been marketed. This apparatus scans a finely focused electron beam with a scan width with a very small interval, detects secondary electrons emitted from the inspection object along with the scan with a secondary electron detector, forms an SEM image, The SEM image is used to compare defects at the same location on different dies to extract defects.

  Conventionally, there has not yet been an apparatus completed as an overall system of defect inspection apparatuses using electron beams.

  By the way, in a defect inspection apparatus to which SEM is applied, a lot of time is required for defect inspection. Further, when the beam current is increased in order to increase the throughput, the beam is blurred due to the space potential effect, and a wafer having an insulator on the surface is charged and a good SEM image cannot be obtained.

  Also, an inspection apparatus that considers the relationship between an electron optical device that inspects by irradiating an electron beam and another subsystem that supplies the inspection object in a clean state up to the irradiation position of the electron optical device and performs alignment Until now, the entire structure has been clarified little. Furthermore, the diameter of the wafer to be inspected has been increased, and there has been a demand for enabling the subsystem to cope with it.

  Therefore, one problem to be solved by the present invention is to use an electron optical system using an electron beam, and to achieve a high throughput by harmonizing the electron optical system with other components constituting the inspection apparatus. It is to provide an improved inspection device.

  Another problem to be solved by the present invention is to improve a loader that transports an inspection object between a cassette that stores the inspection object and a stage device that positions the inspection object with respect to the electron optical system, and an apparatus related to the loader. It is to provide an inspection apparatus capable of inspecting efficiently and accurately.

  Another problem to be solved by the present invention is to provide an inspection apparatus capable of accurately inspecting an object to be inspected by solving a charging problem that has been a problem in SEM.

  Still another problem to be solved by the present invention is to provide a device manufacturing method with a high yield by inspecting an inspection object such as a wafer using the inspection apparatus as described above.

  Conventionally, along with higher density and higher integration of semiconductors, a high-sensitivity inspection apparatus is required for defect inspection of semiconductor wafer patterns and the like in semiconductor wafer process manufacturing. As an inspection apparatus for such a defect inspection, an electron microscope as described in JP-A-2-142045 and JP-A-5-258703 is used.

For example, in an electron microscope described in Japanese Patent Laid-Open No. 2-142045, an electron beam emitted from an electron gun is focused by an objective lens to irradiate the sample, and secondary electrons emitted from the sample are detected by a secondary electron detector. ing. In this electron microscope, a negative voltage is applied to the sample, and an electric field and a magnetic field are orthogonalized between the sample and the secondary electron detector.
A B-type filter is arranged.

With such a configuration, this electron microscope has a high resolution by applying a negative voltage to the sample to decelerate electrons irradiated on the sample.

In addition, by applying a negative voltage to the sample, the secondary electrons emitted from the sample are accelerated, and the accelerated secondary electrons are deflected in the direction of the secondary electron detector by the E × B type filter. Thus, the secondary electron detector can efficiently detect the secondary electrons.

In an apparatus using a conventional electron microscope as described above, the electron beam from the electron gun is accelerated and increased in energy by a lens system such as an objective lens to which a high voltage is applied until immediately before being irradiated onto the sample. Yes. Then, by applying a negative voltage to the sample, the electron irradiated to the sample is slowed down and high resolution is achieved.

However, since a high voltage is applied to the objective lens and a negative voltage is applied to the sample, there is a possibility that a discharge occurs between the objective lens and the sample.

In the conventional electron microscope, even when a negative voltage is not applied to the sample, if the potential difference between the objective lens and the sample is large, a discharge may occur between the objective lens and the sample.

In addition, if the voltage applied to the objective lens is lowered in order to cope with such discharge to the sample, sufficient energy cannot be given to the electrons and the resolution is lowered.

Furthermore, the sample is a semiconductor wafer, and vias are formed on the surface of the semiconductor wafer.
That is, a case will be described in which an upper layer wiring and a lower layer wiring of a semiconductor wafer are electrically connected and there is a wiring pattern in a direction substantially perpendicular to the upper and lower layer wiring surfaces.

When a defect of a semiconductor wafer with vias is inspected using a conventional electron microscope, a high voltage, for example, a voltage of 10 kV is applied to the objective lens as described above. Here, it is assumed that the semiconductor wafer is grounded. Therefore, an electric field is formed between the semiconductor wafer and the objective lens.

In such a state, the electric field is concentrated particularly in the vicinity of the via on the surface of the semiconductor wafer, resulting in a high electric field. When the via is irradiated with an electron beam, a large amount of secondary electrons are emitted from the via, and these secondary electrons are accelerated by a high electric field in the vicinity of the via. The accelerated secondary electrons have sufficient energy (> 3 eV) to ionize the residual gas generated when the semiconductor wafer is irradiated with the electron beam. Therefore, secondary electrons ionize the residual gas, and ionized charged particles are generated.

The positive ions, which are ionized charged particles, are accelerated in the direction of the via by a high electric field near the via and collide with the via, whereby secondary electrons are further emitted from the via. Due to this series of positive feedback, a discharge is finally generated between the objective lens and the semiconductor wafer, and this discharge has a problem of damaging the pattern of the semiconductor wafer.

  Accordingly, another object of the present invention is to provide an electron gun apparatus that prevents discharge to a sample to be inspected, and a device manufacturing method using the electron gun apparatus.

Conventionally, as described above, a defect inspection of a mask pattern for manufacturing a semiconductor device or a pattern formed on a semiconductor wafer is performed by secondary electrons emitted from the sample when the sample surface is irradiated with a primary electron beam. Is detected by obtaining a pattern image of the sample and comparing it with a reference image. Such a defect inspection apparatus is provided with an E × B separator that separates primary electrons and secondary electrons.

FIG. 52 shows a schematic configuration of an example of a projection type electron beam inspection apparatus having an E × B separator. The electron beam emitted from the electron gun 721 is shaped into a rectangle by a shaping opening (not shown), and reduced by an electrostatic lens 722 to form a shaped beam of 1.25 mm square at the center of the E × B separator 723. To do. The shaped beam is deflected so as to be perpendicular to the sample W by the E × B separator 723, and is reduced to 1/5 by the electrostatic lens 724 to irradiate the sample W. The secondary electrons emitted from the sample W have an intensity corresponding to the pattern information on the sample W, and are enlarged by the electrostatic lenses 724 and 741, and the detector 761.
Is incident on. The detector 761 generates an image signal corresponding to the intensity of incident secondary electrons and compares it with a reference image to detect a sample defect.

The E × B separator 723 has a structure in which an electric field and a magnetic field are orthogonal to each other in a plane perpendicular to the normal line of the sample W surface (upward on the paper surface), and the electric field, magnetic field, electron energy and velocity. When the above relationship satisfies a certain condition, the electrons are moved straight, and otherwise, they are deflected. In the inspection apparatus of FIG. 44, the secondary electrons are set so as to go straight.

FIG. 53 shows the movement of the secondary electrons emitted from the rectangular region irradiated with the primary electrons on the sample W surface in more detail. Secondary electrons emitted from the sample surface are magnified by the electrostatic lens 724 and imaged on the center plane 723 a of the E × B separator 723. Since the electric field and magnetic field of the E × B separator 723 are set to such values that the secondary electrons travel straight, the secondary electrons travel straight as they are, and the electrostatic lenses 741-1, 741-2, 741- 3 and is imaged on the target 761a in the detector 761. Then, it is multiplied by an MCP (Multi Channel Plate, not shown), and an image is formed by a scintillator, a CCD (Charge Coupled Device) or the like (not shown). Reference numerals 732 and 733 are aperture stops provided in the secondary optical system.

  FIG. 54 shows a schematic configuration of a conventional E × B separator and a distribution of generated electric fields. An electric field is generated by the two parallel plate electrodes 723-1 and 723-2, and a magnetic field orthogonal to the electric field is generated by the two magnetic poles 723-3 and 723-4. In this configuration, since the magnetic poles 723-3 and 723-4 are made of metal, they have a ground potential, and the electric field is bent toward the ground side. Therefore, the electric field distribution is as shown in FIG. 54, and a parallel electric field can be obtained only in the small region at the center.

When the E × B separator having such a configuration is used for a defect inspection apparatus such as a mapping projection type electron beam inspection apparatus, the electron beam irradiation area cannot be increased in order to perform an accurate inspection. There was a problem of being bad.

  Therefore, another problem to be solved by the present invention is that an area where the electric and magnetic fields are uniform and orthogonal to each other can be enlarged on a plane parallel to the sample, and the overall outer diameter can be reduced. The object is to provide a separator. Another object of the present invention is to use such an E × B separator in a defect inspection apparatus to reduce the aberration of a detected image to be obtained and to efficiently perform an accurate defect inspection.

    In addition, as described above, conventionally, when pattern inspection of a semiconductor wafer or photomask is performed using an electron beam, the electron beam is sent to the surface of a sample such as a semiconductor wafer or photomask, or the sample is scanned, There is known an apparatus for detecting defects by detecting secondary charged particles or the like generated from the surface of the sample, producing image data from the detection result, and comparing data for each cell or die.

However, in the above conventional defect inspection apparatus, the surface of the sample is charged by irradiating the electron beam, and the image data is distorted by the charge due to the charging. In addition, since the distortion of the image data becomes a problem, if the beam current is reduced so that the distortion due to the charge is sufficiently reduced, the S / N ratio of the secondary electron beam signal is deteriorated, and the probability of occurrence of erroneous detection is increased. There is. In addition, there is a problem that throughput is reduced when averaging is performed by scanning a large number of times in order to improve the S / N ratio.

Therefore, another problem to be solved by the present invention is to prevent image distortion due to charging, or to minimize the image distortion even if it occurs, thereby enabling reliable defect inspection. An object of the present invention is to provide an apparatus capable of performing the above and a device manufacturing method using the apparatus.

  Conventionally, the surface of the substrate is irradiated and scanned with a charged particle beam, secondary charged particles generated from the surface of the substrate are detected, image data is created from the detection result, and compared with data for each die. Thus, an apparatus for inspecting a defect or the like of an image formed on the substrate is already known.

  However, in this type of conventional imaging apparatus, including those described in the above publication, the potential distribution on the surface of the substrate to be inspected is not necessarily uniform, and the contrast of the captured image is not sufficient, There was a problem with distortion.

  Accordingly, another problem to be solved by the present invention is to provide an imaging apparatus that improves the defect detection performance without reducing the throughput.

  Another problem to be solved by the present invention is to provide an imaging apparatus that improves the defect detection performance by improving the contrast of an image obtained by detecting secondary electrons from an inspection object.

  In addition, another problem to be solved by the present invention is to reduce the distortion by improving the contrast of the image obtained by detecting secondary electrons from the surface by homogenizing the potential distribution of the surface to be inspected. And providing an imaging device with improved defect detection performance.

  Further, another problem to be solved by the present invention is to provide a device manufacturing method for evaluating a sample in the middle of a process by using the imaging apparatus as described above.

  Conventionally, a defect inspection apparatus for inspecting a defect of a sample by detecting secondary electrons generated by irradiating a sample such as a semiconductor wafer with primary electrons is used in a semiconductor manufacturing process or the like. .

  For example, Japanese Patent Laid-Open No. 11-132975 discloses an electron beam irradiation unit for irradiating a sample with an electron beam, a one-dimensional image of secondary electrons and reflected electrons generated according to changes in the shape, material, and potential of the sample surface, and / or Alternatively, a mapping projection optical unit that forms a two-dimensional image, an electron beam detection unit that outputs a detection signal based on the formed image, an image display unit that displays an electronic image of the sample surface given the detection signal, and an electron Disclosed is a defect inspection apparatus that includes an electron beam deflecting unit that changes an incident angle of an electron beam irradiated from a beam irradiating unit to a sample and an angle at which secondary and reflected electrons are taken into a projection optical unit. ing. According to this defect inspection apparatus, a primary electron beam is irradiated onto a predetermined rectangular area on the surface of a sample wafer of an actual device.

  However, when irradiating an electron beam to a relatively wide area of a sample wafer of an actual device, the sample surface is formed of an insulator such as silicon dioxide or silicon nitride. As a result, secondary electron emission from the sample surface causes the sample surface to be positively charged, and the electric field generated by this potential causes various image defects in the secondary electron beam image.

  The present invention has been made in view of the above-described facts, and it is possible to inspect defects of a sample with higher accuracy by reducing positive charge-up on the surface of the sample and eliminating image obstruction accompanying this charge-up. An object is to provide a defect inspection apparatus and a defect inspection method.

  Furthermore, the present invention provides a semiconductor manufacturing method for improving the yield of device products and preventing shipment of defective products by performing defect inspection of a sample using the defect inspection apparatus as described above in a semiconductor device manufacturing process. Is another purpose.

  Conventionally, an apparatus for irradiating a surface of a sample such as a semiconductor wafer with a charged beam such as an electron beam to expose the surface of the sample with a pattern such as a semiconductor circuit or inspecting a pattern formed on the surface of the sample. Alternatively, in an apparatus that performs ultra-precision processing on a sample by irradiating a charged beam, a stage that accurately positions the sample in a vacuum is used.

When very high-precision positioning is required for such a stage, a structure in which the stage is supported in a non-contact manner by a static pressure bearing is employed. In this case, the vacuum degree of the vacuum chamber is maintained by forming a differential exhaust mechanism in the range of the static pressure bearing to exhaust the high pressure gas so that the high pressure gas supplied from the static pressure bearing is not directly exhausted to the vacuum chamber. is doing.

An example of such a prior art stage is shown in FIG. In the structure shown in the figure, a tip end portion of a lens barrel 71 of a charged beam apparatus that generates a charged beam and irradiates a sample, that is, a charged beam irradiation unit 72 is attached to a housing 98 constituting the vacuum chamber C. The inside of the lens barrel is evacuated by a vacuum pipe 710, and the chamber C is evacuated by a vacuum pipe 911. Then, the charged beam is irradiated from the distal end portion 72 of the lens barrel 71 to the sample W such as a wafer placed therebelow.

  The sample W is detachably held on the sample stage 94 by a known method, and the sample stage 94 is attached to the upper surface of the Y-direction movable portion 95 of the XY stage (hereinafter simply referred to as “stage”) 93. A plurality of static pressure bearings 90 are attached to the Y-direction movable portion 95 on the surfaces of the stage 93 facing the guide surface 96a of the X-direction movable portion 96 (the left and right surfaces and the bottom surface in FIG. 55A). The pressure bearing 90 can move in the Y direction (left and right in FIG. 55 [B]) while maintaining a minute gap with the guide surface. Further, a differential exhaust mechanism is provided around the static pressure bearing so that the high-pressure gas supplied to the static pressure bearing does not leak into the vacuum chamber C. This is shown in FIG. Double grooves 918 and 917 are formed around the hydrostatic bearing 90, and these grooves are always evacuated by a vacuum pipe and a vacuum pump (not shown). With such a structure, the Y-direction movable portion 95 is supported in a non-contact state in a vacuum and can freely move in the Y direction. These double grooves 918 and 917 are formed on the surface of the movable portion 95 where the static pressure bearing 90 is provided so as to surround the static pressure bearing. In addition, since the structure of a static pressure bearing may be a well-known thing, the detailed description is abbreviate | omitted.

  As is apparent from FIG. 55, the X-direction movable portion 96 on which the Y-direction movable portion 95 is mounted has a concave shape that opens upward. The same hydrostatic bearings and grooves are also provided, supported in a non-contact manner with respect to the stage base 97, and can move freely in the X direction.

  By combining the movement of the Y-direction movable portion 95 and the X-direction movable portion 96, the sample W is moved to an arbitrary position in the horizontal direction with respect to the distal end portion of the lens barrel, that is, the charged beam irradiation portion 72, to the desired position of the sample. A charged beam can be irradiated.

  In the stage that combines the above-described static pressure bearing and the differential exhaust mechanism, when the stage moves, the guide surfaces 96a and 97a that oppose the static pressure bearing 90 cause the high-pressure gas atmosphere in the static pressure bearing portion and the vacuum in the chamber. Reciprocates between environments. At this time, on the guide surface, the gas is adsorbed while being exposed to the high-pressure gas atmosphere, and the adsorbed gas is released when exposed to the vacuum environment. For this reason, every time the stage moves, the phenomenon that the degree of vacuum in the chamber C deteriorates occurs, and the above-described processing such as exposure, inspection and processing by the charged beam cannot be performed stably, and the sample is contaminated. There was a problem.

  Therefore, another problem to be solved by the present invention is to provide a charged beam apparatus that can stably perform processing such as inspection and processing with a charged beam by preventing a decrease in the degree of vacuum.

  In addition, another problem to be solved by the present invention is that it has a non-contact support mechanism using a static pressure bearing and a vacuum seal mechanism using differential evacuation, between the irradiation region of the charged beam and the support portion of the static pressure bearing. It is an object of the present invention to provide a charged beam apparatus that generates a pressure difference.

  Another problem to be solved by the present invention is to provide a charged beam device that reduces the gas emitted from the part surface facing the hydrostatic bearing.

  Still another problem to be solved by the present invention is to provide a defect inspection apparatus for inspecting a sample surface using the above charged beam apparatus or an exposure apparatus for drawing a pattern on the surface of the sample.

  Still another problem to be solved by the present invention is to provide a semiconductor manufacturing method for manufacturing a semiconductor device using the above charged beam apparatus.

    Further, in the stage combining the conventional static pressure bearing and the differential exhaust mechanism shown in FIG. 55, since the differential exhaust mechanism is provided, the structure is more complicated than the static pressure bearing stage used in the atmosphere. There is a problem that the size becomes large, the reliability as a stage is low, and the cost is high.

  Therefore, another problem to be solved by the present invention is to provide a charged beam apparatus that is simple in structure and can be made compact by eliminating the differential pumping mechanism of the XY stage.

  Another problem to be solved by the present invention is that a charged beam having a differential evacuation mechanism that evacuates the inside of the housing containing the XY stage and evacuates a region irradiated with the charged beam on the sample surface. Is to provide a device.

  Still another problem to be solved by the present invention is to provide a defect inspection apparatus for inspecting a sample surface using the above charged beam apparatus or an exposure apparatus for drawing a pattern on the surface of the sample.

  Still another problem to be solved by the present invention is to provide a semiconductor manufacturing method for manufacturing a semiconductor device using the above charged beam apparatus.

  Further, as described above, conventionally, a defect inspection apparatus for inspecting a defect of a sample by detecting secondary electrons generated by irradiating a sample such as a semiconductor wafer with primary electrons is a semiconductor manufacturing process or the like. It is used in.

  Such a defect inspection apparatus includes a technique that applies image recognition technology to automate and increase the efficiency of defect inspection. In this technique, the pattern image data of the inspected area on the sample surface acquired by detecting secondary electrons and the reference image data of the sample surface stored in advance are matched by a computer, and based on the calculation result, The specimen is automatically judged for defects.

  In recent years, especially in the field of semiconductor manufacturing, higher definition of patterns has progressed, and the need to detect fine defects has increased. Under such circumstances, a further improvement in recognition accuracy is required even in a defect inspection apparatus to which the above image recognition technology is applied.

However, in the above prior art, a positional deviation occurs between the secondary electron beam image acquired by irradiating the inspection surface of the sample surface with the primary electron beam and the reference image prepared in advance, and defect detection is performed. There was a problem of reducing accuracy. This misalignment becomes a particularly serious problem when the irradiation area of the primary electron beam is displaced from the wafer and a part of the inspection pattern is missing from the detection image of the secondary electron beam. It cannot be dealt with by optimization technology alone. This can be a fatal defect especially in the inspection of high definition patterns.

Accordingly, another object of the present invention is to provide a defect inspection apparatus that prevents a decrease in defect inspection accuracy due to a displacement between an image to be inspected and a reference image.

Furthermore, the present invention provides a semiconductor manufacturing method for improving the yield of device products and preventing shipment of defective products by performing defect inspection of a sample using the defect inspection apparatus as described above in a semiconductor device manufacturing process. Is another purpose.

  The present invention utilizes a method called a mapping projection method using an electron beam as a method for improving the inspection speed, which is basically a drawback of the SEM method. The mapping projection method will be described below.

  The projection projection method irradiates the observation area of the sample with the primary electron beam at once (irradiates a certain area without scanning), and the secondary electron from the irradiated area is collectively detected by the lens system (detector). An image of an electron beam is formed on a microchannel plate + a fluorescent plate. The image information is converted into an electrical signal by a two-dimensional CCD (solid-state imaging device) or TDI-CCD (line image sensor), and is output on a CRT or stored in a storage device. From this image information, a defect of the sample wafer (semiconductor (Si) wafer in the process) is detected. In the case of a CCD, the moving direction of the stage is the short axis direction (the long axis direction may be sufficient), and the movement is a step-and-repeat method. In the case of TDI-CCD, the stage is moved continuously in the integration direction. Since images can be continuously acquired with TDI-CCD, TDI-CCD is used when performing defect inspection continuously. The resolution is determined by the magnification and accuracy of the imaging optical system (secondary optical system). In the embodiment, a resolution of 0.05 μm is obtained. In this example, when the resolution is 0.1 μm and the electron beam irradiation condition is 1.6 μA in the region of 200 μm × 50 μm, the inspection time is about 1 hour per 20 cm wafer, which is 8 times that of the SEM method. ing. The specifications of the TDI-CCD used here are 2048 pixels (pixels) × 512 stages, and the line rate is 3.3 μs (line frequency 300 kHz).

  Although the irradiation area in this example matches the specification of TDI-CCD, the irradiation area may be changed depending on the irradiation object.

  The problems with this mapping method are: (1) Easy to charge up on the sample surface to irradiate the electron beam at once, (2) There is a limit to the electron beam current obtained by this method (about 1.6μA) inspection It is a hindrance to speed improvement.

   In order to solve the above-described conventional problems, the first invention of the present application irradiates the target with an electron beam emitted from the electron gun, detects the electron emitted from the target using a detector, and An image pickup apparatus that collects image information, inspects a defect of a target, and the like includes means for uniformizing or reducing charges charged on the target.

    According to a second aspect of the present invention, in the imaging apparatus according to the first aspect, the means includes an electrode that is disposed between the electron gun and the object and that can control the charged electric charge. To do.

    The third invention of the present application is characterized in that, in the image pickup apparatus of the first invention, the means operates in an idle time of the measurement timing.

A fourth invention of the present application is a defect inspection apparatus for inspecting a defect of a sample,
An electron beam irradiation means capable of irradiating the sample with a primary electron beam;
Mapping projection means for mapping and imaging a secondary electron beam emitted from the sample by irradiation of the primary electron beam; and
Detecting means for detecting an image formed by the mapping projection means as an electronic image of the sample;
Defect determining means for determining a defect of the sample based on the electronic image detected by the detecting means;
Including
Electrons having lower energy than the primary electron beam are supplied to the sample at least within a period in which the detection unit detects the electronic image.

A fifth invention of the present application includes at least one or more primary optical systems for irradiating a sample with a plurality of primary charged particle beams, and at least one or more secondary optical systems for guiding secondary charged particles to at least one or more detectors. The plurality of primary charged particle beams are irradiated to positions separated from each other by a distance resolution of the secondary optical system,
Defect determination means for determining a defect of the sample based on an image of secondary charged particles detected by the at least one detector;
Charged particle supply means for supplying charged particles having energy lower than that of the primary charged particle beam to the sample;
Is further included.

The sixth invention of the present application is a defect inspection method for inspecting a defect of a sample,
Irradiating the sample with a primary electron beam;
A mapping projection step of mapping and projecting a secondary electron beam emitted from the sample by irradiation of the primary electron beam; and
A detection step of detecting an image formed in the mapping projection step as an electronic image of the sample;
A defect determination step of determining a defect of the sample based on the electronic image detected in the detection step;
Including
Electrons having energy lower than that of the primary electron beam are supplied to the sample at least within a period in which the electronic image is detected in the detection step.

The seventh invention of the present application is a defect inspection method for inspecting a defect of a sample,
An electron beam irradiation step of irradiating the sample with a primary electron beam;
A mapping projection step of mapping and projecting a secondary electron beam emitted from the sample by irradiation of the primary electron beam; and
A detection step of detecting an image formed in the mapping projection step as an electronic image of the sample;
A defect determination step of determining a defect of the sample based on the electronic image detected in the detection step;
Including
The method further includes a UV photoelectron supply step of supplying UV photoelectrons to the sample.

     An eighth invention of the present application includes an electron irradiation unit, a lens system, a deflector, an EXB filter, and an electron detector, and an electron beam from the electron irradiation unit is passed through the lens system, the deflector, and the EXB filter. In a projection type electron beam inspection apparatus that irradiates an inspection area, forms an electron generated from a sample on the electron detector by the lens system, deflector, and EXB filter, and inspects the electric signal as an image, immediately before the inspection. A charged particle irradiation unit for irradiating a region to be inspected with charged particles in advance is provided.

    According to a ninth aspect of the present invention, in the apparatus according to the eighth aspect, the charged particles are electrons, positive or negative ions, or plasma.

    According to a tenth aspect of the present invention, in the apparatus according to the eighth or ninth aspect, the energy of the charged particles is 100 eV or less.

    The eleventh invention of the present application is characterized in that, in the apparatus of the eighth or ninth invention, the energy of the charged particles is 30 eV or less.

      The first embodiment of the present application is a working chamber for inspecting an inspection object, which can be controlled in a vacuum atmosphere, in an inspection apparatus for inspecting the inspection object by irradiating one of charged particles or electromagnetic waves to the inspection object; Beam generating means for generating one of charged particles or electromagnetic waves as a beam, and guiding and irradiating the beam to the inspection object held in the working chamber, detecting secondary charged particles generated from the inspection object, and image processing An electron optical system that leads to a system; an image processing system that forms an image with the secondary charged particles; an information processing system that displays and / or stores state information of an inspection object based on the output of the image processing system; And a stage device that holds an inspection target so as to be movable relative to the beam.

  The second embodiment of the present application is characterized in that, in the detection apparatus of the first embodiment, an inspection mechanism is maintained and a loading / unloading mechanism for loading / unloading the working chamber is provided.

The third embodiment of the present application is the mini-environment device according to the second embodiment of the present application, wherein the carry-in / out mechanism causes a clean gas to flow through the inspection target to prevent dust from adhering to the inspection target. And at least two loading chambers disposed between the mini-environment device and the working chamber, each of which can be independently controlled to a vacuum atmosphere, the mini-environment device, and the loading chamber, A loader having a transfer unit capable of transferring the inspection object between and a separate transfer unit capable of transferring the inspection object between the inside of the one loading chamber and the stage device,
The working chamber and the loading chamber are supported via a vibration isolator.

The fourth embodiment of the present application is the inspection apparatus of the first embodiment of the present application,
A loader for supplying the inspection object onto the stage apparatus in the working chamber;
A precharge unit that irradiates the inspection target disposed in the working chamber with charged particles to reduce charging unevenness of the inspection target, and a potential applying mechanism that applies a potential to the inspection target. And

  According to a fifth embodiment of the present application, in the inspection apparatus according to the third embodiment, the loader includes a first loading chamber and a second loading chamber in which the atmosphere can be independently controlled, and the inspection. A first transfer unit for transferring an object between the inside of the first loading chamber and the outside thereof; and the second loading chamber, the inspection object being provided in the first loading chamber and the stage device. And a second transport unit for transporting to and from the top.

In a sixth embodiment of the present application, in the inspection apparatus according to the first, second, or third embodiment, alignment is further performed by observing the surface of the inspection object for positioning the inspection object with respect to the electron optical system. An alignment control device that controls the coordinates of the inspection object on the stage device, and a laser interference distance measuring device that detects the coordinates of the inspection object on the stage device. It is characterized by determining.

The seventh embodiment of the present application is the inspection apparatus according to the first, second or third embodiment, wherein the alignment of the inspection object is a rough alignment performed in the mini-environment space, and the stage apparatus. XY direction alignment and rotation direction alignment performed above are included.

An eighth embodiment of the present application is the inspection apparatus according to any one of the first, second, and third embodiments, wherein the electron optical system is
An E × B deflector that deflects the secondary charged particles toward the detector by a field in which an electric field and a magnetic field are orthogonal to each other;
It is arranged between the decelerating electric field type objective lens and the sample to be inspected, and has a shape substantially axisymmetric with respect to the irradiation optical axis of the beam, and the electric field intensity on the irradiation surface of the electron beam of the sample to be inspected. An electrode to be controlled is provided.

The ninth embodiment of the present application is an inspection apparatus according to any one of the first, second, and third embodiments, in which the apparatus performs secondary charging in which the charged particles and the charged particles travel in a substantially opposite direction. An E × B separator that selectively deflects the charged particles or the secondary charged particles, and the electrodes for generating an electric field are composed of three or more pairs of nonmagnetic conductor electrodes. And an E × B separator arranged to form a substantially cylindrical shape.

The tenth embodiment of the present application is an inspection apparatus according to any one of the first, second, and third embodiments, in which the apparatus irradiates a region to be inspected immediately before the inspection with charged particles in advance. It has the part.

    An eleventh embodiment of the present application is an inspection apparatus according to any one of the first, second, and third embodiments, and the apparatus includes means for equalizing or reducing charges charged on the inspection object. It is characterized by having.

    The twelfth embodiment of the present application is an inspection apparatus according to any one of the first, second, and third embodiments, wherein the apparatus is at least within a period in which the detection means detects the secondary charged particle image. In addition, electrons having lower energy than the charged particles are supplied to the sample.

The thirteenth embodiment of the present application is an inspection apparatus according to any one of the first, second, and third embodiments, wherein the stage is an XY stage, and the XY stage is housed in a working chamber and is static. It is supported in non-contact with the working chamber by the pressure bearing,
The working chamber containing the stage is evacuated,
A differential evacuation mechanism is provided around the portion of the charged particle beam device that irradiates the charged particle beam on the sample surface to exhaust the region irradiated with the charged particle beam on the sample surface. And

A fourteenth embodiment of the present application is an inspection apparatus according to any one of the first, second, and third embodiments, wherein the apparatus places a sample on an XY stage, and the sample is placed in a vacuum. It has a device that moves to an arbitrary position and irradiates a charged particle beam to the sample surface
The XY stage is provided with a non-contact support mechanism by a static pressure bearing and a vacuum seal mechanism by differential exhaust,
A partition having a small conductance is provided between a portion irradiated with the charged particle beam on the sample surface and the static pressure bearing support portion of the XY stage,
A pressure difference is generated between the charged particle beam irradiation region and the static pressure bearing support portion.

The fifteenth embodiment of the present application is an inspection apparatus according to any one of the first, second, and third embodiments,
Image acquisition means for acquiring images of a plurality of regions to be inspected that are displaced from each other while partially overlapping on the sample;
Storage means for storing a reference image;
Defect determination means for determining defects of the sample by comparing the images of the plurality of inspected areas acquired by the image acquisition means and the reference image stored in the storage means;
It is characterized by including.

  The sixteenth embodiment of the present application is characterized in that a defect in a wafer during or after the process is detected using the inspection apparatus of the first to fifteenth embodiments in the device manufacturing method.

According to Example 1-16 of the present application, the following effects can be obtained.
(A) An overall configuration of a mapping projection type inspection apparatus using charged particles can be obtained, and an inspection object can be processed with high throughput.
(B) Inspecting the inspection object while monitoring the dust in the space by providing a sensor for preventing the adhesion of dust by flowing clean gas to the inspection object in the mini-environment space and observing the cleanliness. Can do.
(C) Since the loading chamber and the working chamber are integrally supported via the vibration preventing device, it is possible to supply and inspect the inspection target to the stage device without being affected by the external environment.
(D) Since a precharge unit is provided, a wafer made of an insulator is not easily affected by charging.

A seventeenth embodiment of the present application includes a beam generator for irradiating a specimen with charged particles,
A decelerating electric field type objective lens for decelerating the charged particles and accelerating secondary charged particles generated by irradiating the sample to be inspected with the charged particles;
A detector for detecting the secondary charged particles;
An E × B deflector that deflects the secondary charged particles toward the detector by a field in which an electric field and a magnetic field are orthogonal to each other;
The electric field intensity on the irradiation surface of the charged sample of the sample to be inspected, which is disposed between the decelerating electric field type objective lens and the sample to be inspected and has a shape substantially axisymmetric with respect to the irradiation optical axis of the charged particle. It is characterized by comprising an electrode for controlling the above.

  The eighteenth embodiment of the present application is characterized in that, in the inspection apparatus of the seventeenth embodiment, a voltage applied to the electrode is controlled according to the type of the sample to be inspected in order to control the electric field strength. .

  In the nineteenth embodiment of the present application, in the inspection apparatus according to the seventeenth embodiment, the sample to be inspected is a semiconductor wafer, and a voltage applied to the electrode to control the electric field strength is It is controlled by the presence or absence of vias.

A twentieth embodiment of the present application is a device manufacturing method using the inspection apparatus according to any of the seventeenth to nineteenth embodiments,
A defect of the semiconductor wafer which is the sample to be inspected is inspected using the inspection apparatus in the course of device manufacture.

  According to the embodiment of the present application No. 17-20, the following effects can be obtained.

  Between the specimen to be inspected and the objective lens, it has a shape substantially axisymmetric with respect to the irradiation axis of the charged particles, and has an electrode for controlling the electric field strength on the irradiation surface of the charged particles of the specimen to be inspected. The electric field between the sample to be inspected and the objective lens can be controlled.

  In addition, an electrode is provided between the sample to be inspected and the objective lens, the electrode being substantially axisymmetric with respect to the irradiation axis of the charged particle and weakening the electric field intensity on the charged particle irradiation surface of the sample to be inspected. Therefore, the discharge between the sample to be inspected and the objective lens can be eliminated.

  In addition, since the applied voltage to the objective lens is not changed and the like is not changed, the secondary charged particles can be efficiently passed through the objective lens, so that the detection efficiency is improved and a signal with a good S / N ratio is obtained. Can do.

  Moreover, the voltage for weakening the electric field intensity on the charged particle irradiation surface of the sample to be inspected can be controlled depending on the type of the sample to be inspected.

For example, when the sample to be inspected is a type of sample to be inspected that easily discharges from the objective lens, the voltage of the electrode is changed to make the electric field strength on the charged particle irradiation surface of the sample to be inspected weaker. Thus, discharge can be prevented.

Also, depending on the presence or absence of vias in the semiconductor wafer, the voltage applied to the electrodes is changed.
That is, the voltage for weakening the electric field intensity on the electron beam irradiation surface of the semiconductor wafer can be changed.

For example, if the sample to be inspected is a type of sample to be inspected that is easily discharged between the objective lens, the electric field intensity at the charged particle irradiation surface of the sample to be inspected is made weaker by changing the electric field by the electrode. Thus, it is possible to prevent discharge particularly in the via and the periphery of the via.

In addition, since discharge between the via and the objective lens can be prevented, the pattern of the semiconductor wafer or the like is not damaged by discharge.

In addition, since the potential applied to the electrode is lower than the charge applied to the sample to be inspected, the electric field strength at the charged particle irradiation surface of the sample to be inspected can be weakened, and discharge to the sample to be inspected can be prevented.

Further, since the potential applied to the electrode is set to a negative potential and the sample to be inspected is grounded, the electric field strength at the charged particle irradiation surface of the sample to be inspected can be weakened and discharge to the sample to be inspected can be prevented.

In the twenty-first embodiment of the present application, a first charged particle beam and a second charged particle beam traveling in a direction substantially opposite to the first charged particle beam are incident, and the first charged particle beam is incident. Or an E × B separator that selectively deflects the second charged particle beam,
An electrode for generating an electric field is composed of three or more pairs of nonmagnetic conductor electrodes, and is arranged so as to form a substantially cylindrical shape.

The twenty-second embodiment of the present application is the E × B separator of the twenty-first embodiment,
A parallel plate magnetic pole for generating a magnetic field is disposed outside a cylinder formed by the three or more pairs of nonmagnetic conductor electrodes, and a protrusion is formed on the periphery of the opposing surface of the parallel plate electrode.

The twenty-third embodiment of the present application is the E × B separator of the twenty-second embodiment,
Of the paths of the generated magnetic field lines, most of the paths other than between the parallel plate magnetic poles have a cylindrical shape coaxial with the cylinder formed by the three or more pairs of nonmagnetic conductor electrodes.

The twenty-fourth embodiment of the present application is the E × B separator according to the twenty-second or twenty-third embodiment,
The parallel plate magnetic pole is a permanent magnet.

The twenty-fifth embodiment of the present application is an inspection apparatus using the E × B separator according to any of the twenty-first to twenty-fourth embodiments,
One of the first charged particle beam or the second charged particle beam is a primary charged particle beam that irradiates the sample to be inspected, and the other 2 is generated from the sample by irradiation of the primary charged particle beam. It is a secondary charged particle beam.

  According to the twenty-first to twenty-fifth embodiments of the present application, the following effects can be obtained.

  A region where both the electric and magnetic fields are uniform around the optical axis can be made large, and even if the irradiation range of the charged particles is widened, the aberration of the image passing through the E × B separator is set to a value with no problem. Can do.

  In addition, since the protrusion is provided in the periphery of the magnetic pole that forms the magnetic field and this magnetic pole is provided outside the electric field generating electrode, a uniform magnetic field can be generated and the electric field distortion due to the magnetic pole can be reduced. Further, since the magnetic field is generated using the permanent magnet, the entire E × B separator can be stored in a vacuum. Furthermore, the entire E × B separator can be miniaturized by forming the electric field generating electrode and the magnetic path forming magnetic circuit into a coaxial cylindrical shape with the optical axis as the central axis.

  A twenty-sixth embodiment of the present application includes a charged particle irradiation unit, a lens system, a deflector, an EXB filter (Wien filter), and a secondary charged particle detector, and charged particles are supplied from the charged particle irradiation unit to the lens. System, deflector, irradiate the inspection area of the sample through the EXB filter, and image the secondary charged particles generated from the sample on the secondary charged particle detector by the lens system, deflector, EXB filter, In a projection type electron beam inspection apparatus that inspects the electrical signal as an image, a charged particle irradiation unit that irradiates a region to be inspected immediately before the inspection with charged particles is provided.

  The twenty-seventh embodiment of the present application is characterized in that, in the apparatus of the twenty-sixth embodiment, the charged particles are electrons, positive or negative ions, or plasma.

  The twenty-eighth embodiment of the present application is characterized in that, in the apparatus of the twenty-sixth or twenty-seventh embodiment, the energy of the charged particles is 100 eV or less.

  The twenty-ninth embodiment of the present application is characterized in that, in the apparatus of the twenty-sixth or twenty-seventh embodiment, the energy of the charged particles is 30 eV or less.

The thirtieth embodiment of the present application is characterized in that, in the device manufacturing method, pattern inspection is performed during the device manufacturing process using the inspection apparatus according to any of the twenty-sixth to twenty-ninth embodiments. To do.
According to the embodiment of the present application No. 26-30, the following effects can be obtained.

    Since the measurement image distortion due to charging does not occur or is slight due to the processing immediately before measurement by charged particle irradiation, the defect can be measured correctly.

In addition, since the stage can be scanned by passing a large amount of current that has been problematic in the past, a large amount of secondary electrons can be detected, a detection signal with a good S / N ratio can be obtained, and the reliability of defect detection Will improve.
Further, since the S / N ratio is large, good image data can be produced even if the stage is scanned earlier, and the inspection throughput can be increased.

  The thirty-first embodiment of the present application irradiates a target with charged particles emitted from a beam generator, detects secondary charged particles emitted from the target using a detector, and detects the image information of the target. An image pickup apparatus that performs collection, inspection of a defect of a target, and the like includes a unit that equalizes or reduces charges charged on the target.

  According to a thirty-second embodiment of the present application, in the imaging apparatus according to the thirty-first embodiment, the means is disposed between the beam generator and the object, and the charged electric charge can be controlled. It is characterized by providing an electrode.

  The thirty-third embodiment of the present application is characterized in that, in the image pickup apparatus of the thirty-first embodiment, the means operates in a vacant time of measurement timing.

  In a thirty-fourth embodiment of the present application, in the imaging apparatus according to the thirty-first embodiment, at least one primary optical system that irradiates the target with a plurality of charged particle beams, and electrons emitted from the target And at least one secondary optical system that guides to at least one detector, and the plurality of primary charged particle beams are irradiated to positions separated from each other by a distance resolution of the secondary optical system. Features.

A thirty-fifth embodiment of the present application includes a step of detecting a defect of a wafer during or after the process using the imaging apparatus according to the thirty-first to thirty-fourth embodiments in a device manufacturing method. It is characterized by.
According to the example of the present application No. 31-35, the following effects can be obtained.
(A) Image distortion caused by charging can be reduced regardless of the properties of the inspection object.
(B) Since the charging is made uniform and offset using the idle time of the conventional measurement timing, the throughput is not affected at all.
(C) Since real-time processing is possible, post-processing time and memory are not required.
(D) High-speed and high-accuracy image observation and defect detection are possible.

  In the thirty-sixth embodiment of the present application, a charged particle irradiating means capable of irradiating a sample with primary charged particles and a map for projecting secondary charged particles emitted from the sample by irradiation of the primary charged particles to form an image. A projecting unit; a detecting unit that detects an image formed by the mapping projecting unit as an electronic image of the sample; and a defect determining unit that determines a defect of the sample based on the electronic image detected by the detecting unit. The electron beam having energy lower than that of the irradiated primary charged particles is supplied to the sample at least within a period in which the detection means detects the electronic image.

  In the thirty-seventh embodiment, the charged particle irradiating means irradiates the sample with primary charged particles, and the mapping projection means maps and projects the secondary charged particles emitted from the sample by the irradiation of the primary charged particles to form the detecting means. Let me image. The sample from which the secondary charged particles are released is charged up to a positive potential. The detection unit detects the image formed as an electronic image of the sample, and the defect determination unit determines a defect of the sample based on the detected electronic image. In this case, electrons having lower energy than the irradiated primary charged particles are supplied to the sample at least within a period in which the detection means detects the electronic image. This low energy electron electrically neutralizes the positively charged sample by the emission of secondary charged particles. Thus, the secondary charged particles are imaged without being substantially affected by the positive potential of the sample, and the detection means can detect an electronic image with reduced image disturbance.

  For example, UV photoelectrons are preferably used as lower energy electrons than the primary charged particles. UV photoelectrons refer to electrons emitted in accordance with the photoelectric effect by irradiating a substance such as metal with a light beam including ultraviolet rays (UV). Further, low energy electrons may be generated by means of low energy electron generation means that is separate from the charged particle irradiation means, such as an electron gun.

  Among the electrons emitted from the sample by the irradiation of the primary charged particles, in addition to the secondary charged particles generated by the electrons in the sample being emitted from the surface by the collision of the primary charged particles, the primary charged particles are also emitted from the sample surface. Reflected electrons generated by reflection are also included. Of course, the electronic image detected by the detection means of the present embodiment also includes such contribution due to reflected electrons.

  The thirty-seventh embodiment of the present application is directed to a charged particle irradiating means capable of irradiating a sample with primary charged particles, and a mapping for projecting secondary charged particles emitted from the sample by irradiation of the primary charged particles to form an image. A projecting unit; a detecting unit that detects an image formed by the mapping projecting unit as an electronic image of the sample; a defect determining unit that determines a defect of the sample based on the electronic image detected by the detecting unit; and the sample Further comprising UV photoelectron supply means capable of supplying UV photoelectrons.

  In the thirty-seventh embodiment, as long as the UV photoelectron supply means (or in the UV photoelectron supply) can achieve the effect of reducing the image disturbance of this embodiment, low energy can be used at any timing and in any period. Electrons are supplied to the sample. For example, even if the supply of UV photoelectrons is started at any timing before execution of primary charged particle irradiation or before execution of secondary charged particle imaging, or after secondary charged particle imaging and before electronic image detection. Good. Further, as in the embodiment of FIG. 24, the UV photoelectron supply may be continued at least during the period of detection of the secondary charged particles, but the sample is sufficiently electrically even before or during the detection of the electronic image. Once summed, UV photoelectrons may be stopped.

  A thirty-eighth embodiment of the present application is a defect inspection method for inspecting a defect of a sample, the step of irradiating the sample with primary charged particles, and a step of irradiating the sample with the primary charged particles. A mapping projection step of mapping and projecting the next charged particles, a detection step of detecting the image formed in the mapping projection step as an electronic image of the sample, and the electronic image detected in the detection step A defect determination step of determining a defect of the sample based on the electron beam, and supplying electrons having lower energy than the primary charged particles to the sample at least within a period of detecting the electronic image in the detection step. It is characterized by.

The 39th embodiment of the present application is an inspection method for inspecting a defect of a sample,
A charged particle irradiation step of irradiating the sample with primary charged particles, a mapping projection step of mapping and projecting secondary charged particles emitted from the sample by irradiation of the primary charged particles, and a mapping projection step. A detection step of detecting the imaged image as an electronic image of the sample, and a defect determination step of determining a defect of the sample based on the electronic image detected in the detection step. The method further includes a UV photoelectron supply step for supplying the light.

A forty-fourth embodiment of the present application includes a step of inspecting a defect of a sample necessary for manufacturing a semiconductor device by using the inspection apparatus according to the thirty-sixth or thirty-seventh embodiment in a semiconductor manufacturing method. It is characterized by including.
According to the thirty-sixth to thirty-sixth embodiment of the present application, the following effects can be obtained.

  Since electrons having lower energy than the primary charged particles are supplied to the sample, the positive charge-up of the sample surface due to the discharge of the secondary charged particles is reduced. Thus, an excellent effect is obtained that it is possible to inspect defects of the sample with higher accuracy.

  Further, if the defect inspection of the sample is performed using the above-described defect inspection apparatus in the device manufacturing method, an excellent effect that the yield of products and the shipment of defective products can be prevented can be obtained.

The forty-first embodiment of the present application is an apparatus in which a sample is placed on an XY stage, the sample is moved to an arbitrary position in a vacuum, and a charged particle beam is irradiated on the sample surface.
The XY stage is provided with a non-contact support mechanism by a static pressure bearing and a vacuum seal mechanism by differential exhaust,
A partition having a small conductance is provided between a portion irradiated with the charged particle beam on the sample surface and the static pressure bearing support portion of the XY stage,
A pressure difference is generated between the charged particle beam irradiation region and the static pressure bearing support portion.

  The forty-second embodiment of the present application is the charged particle beam apparatus according to the forty-first embodiment, wherein the partition incorporates a differential exhaust structure.

  The forty-third embodiment of the present application is the charged particle beam device according to the forty-first or forty-second embodiment, wherein the partition has a cold trap function.

  The forty-fourth embodiment of the present application is the charged particle beam device according to any of the forty-first to forty-third embodiments, wherein the partition is in the vicinity of the charged particle beam irradiation position and in the vicinity of the static pressure bearing. It is provided in two places.

  In the forty-fifth embodiment of the present application, in the charged particle beam apparatus according to any of the forty-first to forty-fourth embodiments, the gas supplied to the static pressure bearing of the XY stage is nitrogen or non-volatile. It is an active gas.

  According to a forty-sixth embodiment of the present application, in the charged particle beam apparatus according to any one of the forty-first to forty-fifth embodiments, an emission gas is generated on at least a part surface of the XY stage facing a static pressure bearing. It is characterized by having been subjected to a surface treatment for reducing.

  The forty-seventh embodiment of the present application is characterized in that a wafer defect inspection apparatus for inspecting defects on the surface of a semiconductor wafer is configured by using the apparatus of any of the forty-first to forty-sixth embodiments. And

  The forty-eighth embodiment of the present application constitutes an exposure apparatus for drawing a circuit pattern of a semiconductor device on the surface of a semiconductor wafer or a reticle, using the apparatus of any of the forty-first to forty-sixth embodiments. It is characterized by that.

The forty-ninth embodiment of the present application is characterized in that a semiconductor is manufactured by using the apparatus of the forty-first to forty-eighth embodiments in a semiconductor manufacturing method.
According to the embodiments of the present application No. 41-49, the following effects can be obtained.
(A) The stage device can exhibit highly accurate positioning performance in a vacuum, and the pressure at the charged particle beam irradiation position is unlikely to increase. That is, the processing with the charged particle beam can be performed on the sample with high accuracy.
(B) Gas released from the static pressure bearing support can hardly pass through the partition to the charged particle beam irradiation region side. As a result, the degree of vacuum at the charged particle beam irradiation position can be further stabilized.
(C) It becomes difficult for the emitted gas to pass to the charged particle beam irradiation region side, and the degree of vacuum in the charged particle beam irradiation region can be easily maintained stably.
(D) The inside of the vacuum chamber is divided into three chambers, a charged particle beam irradiation chamber, a static pressure bearing chamber, and an intermediate chamber thereof, through a small conductance. Then, the evacuation system is configured so that the pressure in each chamber becomes the charged beam irradiation chamber, the intermediate chamber, and the static pressure bearing chamber in order from the lowest. The pressure fluctuation to the intermediate chamber is further suppressed by the partition, and the pressure fluctuation to the charged particle beam irradiation chamber is further reduced by the other partition, and the pressure fluctuation can be reduced to a level that is not substantially problematic. Become.
(E) It becomes possible to suppress the pressure rise when the stage moves.
(F) It is possible to further suppress the pressure increase when the stage moves.
(G) Since the stage positioning performance can be realized with high accuracy and the inspection device with stable vacuum degree of the charged particle beam irradiation area can be realized, an inspection device with high inspection performance and no risk of contaminating the sample. Can be provided.
(H) Since an exposure apparatus with high stage positioning performance and a stable degree of vacuum in the charged particle beam irradiation area can be realized, an exposure apparatus with high exposure accuracy and no risk of contaminating the sample is provided. can do.
(L) A fine semiconductor circuit can be formed by manufacturing a semiconductor with an apparatus having high accuracy in positioning of the stage and a stable degree of vacuum in the charged particle beam irradiation region.

A fifty embodiment of the present application is an inspection apparatus and method for inspecting a defect of a sample,
Image acquisition means for acquiring images of a plurality of regions to be inspected that are displaced from each other while partially overlapping on the sample;
Storage means for storing a reference image;
Defect determination means for determining defects of the sample by comparing the images of the plurality of inspected areas acquired by the image acquisition means and the reference image stored in the storage means;
It is characterized by including.

According to a fifty-first embodiment of the present application, in the inspection apparatus and method according to the fifty-first embodiment, a plurality of regions to be inspected are each irradiated with a primary charged particle beam, and a secondary charged particle beam is emitted from the sample. A charged particle irradiation means for causing
The image acquisition means sequentially acquires images of the plurality of regions to be inspected by detecting secondary charged particle beams emitted from the plurality of regions to be inspected.

The fifty-second embodiment of the present application is the inspection apparatus and method according to the fifty-first embodiment, wherein the charged particle irradiation means
A particle source for emitting primary charged particles, and a deflecting means for deflecting the primary charged particles,
The primary charged particles emitted from the particle source are deflected by the deflecting unit to sequentially irradiate the plurality of regions to be inspected with the primary charged particles.

A fifty-third embodiment of the present application includes a primary optical system that irradiates a sample with a primary charged particle beam in the inspection apparatus and method according to the fifty-second to fifty-second embodiments;
And a secondary optical system for guiding secondary charged particles to a detector.

  The fifty-fourth embodiment of the present application is a process for inspecting a semiconductor manufacturing method for defects in a wafer during processing or a finished product using the inspection apparatus according to any of the fifty-fifth to thirty-third embodiments. It is characterized by including.

  According to the embodiment of the present application No. 50-54, the following effects can be obtained.

  Inspecting a sample for defects by acquiring images of a plurality of inspected regions that are displaced from each other while partially overlapping on the sample, and comparing the images of these inspected regions with a reference image Therefore, it is possible to obtain an excellent effect that it is possible to prevent the defect inspection accuracy from being lowered due to the positional deviation between the inspection image and the reference image.

  Further, according to the device manufacturing method of the present embodiment, since the defect inspection of the sample is performed using the defect inspection apparatus as described above, it is possible to improve the yield of the product and prevent the shipment of the defective product. An effect is obtained.

  The 55th embodiment of the present application is an apparatus for irradiating a specimen placed on an XY stage with a charged particle beam, the XY stage being accommodated in the housing and not contacting the housing by a static pressure bearing. The housing in which the stage is accommodated is evacuated, and the charged beam on the sample surface is irradiated around the portion of the charged particle beam device that irradiates the charged particle beam on the sample surface. The present invention is characterized in that a differential exhaust mechanism for exhausting the region to be discharged is provided.

  According to this embodiment, the high-pressure gas for hydrostatic bearing leaking into the vacuum chamber is first exhausted by the vacuum exhaust pipe connected to the vacuum chamber. And by providing a differential pumping mechanism that exhausts the region irradiated with the charged particle beam around the portion irradiated with the charged particle beam, the pressure in the charged particle beam irradiation region is greatly reduced from the pressure in the vacuum chamber, It is possible to stably achieve a degree of vacuum at which a sample can be processed without problems with a charged particle beam. In other words, a stage having a structure similar to that of a static pressure bearing type stage generally used in the atmosphere (a stage supporting a static pressure bearing without a differential pumping mechanism) is used to charge the sample on the stage. Processing with a particle beam can be performed stably.

  The fifty-sixth embodiment of the present application is the charged particle beam apparatus according to the fifty-fifth embodiment, wherein the gas supplied to the static pressure bearing of the XY stage is nitrogen or an inert gas. The active gas is pressurized after being exhausted from the housing that houses the stage, and is supplied again to the static pressure bearing.

  According to this embodiment, since the residual gas component in the vacuum housing becomes a high purity inert gas, the sample surface and the surface of the structure in the vacuum chamber formed by the housing are contaminated with moisture and oil. There is no fear, and even if inert gas molecules are adsorbed on the sample surface, if they are exposed to the differential pumping mechanism or the high vacuum part of the charged particle beam irradiation region, they will quickly leave the sample surface, so the charged particle beam It is possible to minimize the influence on the degree of vacuum of the irradiation region, and it is possible to stabilize the processing of the sample by the charged particle beam.

  The fifty-seventh embodiment of the present application is a wafer defect inspection apparatus for inspecting a semiconductor wafer surface for defects using the apparatus of the fifty-fifth or fifty-sixth embodiment.

  Thereby, it is possible to provide an inspection apparatus with high stage positioning performance and a stable degree of vacuum in the irradiation region of the charged particle beam at a low cost.

  The fifty-eighth embodiment of the present application is an exposure apparatus for drawing a circuit pattern of a semiconductor device on the surface of a semiconductor wafer or a reticle using the apparatus of the fifty-fifth or fifty-sixth embodiment.

  Thereby, it is possible to provide an exposure apparatus with high stage positioning performance and a stable degree of vacuum in the charged beam irradiation region at low cost.

  The fifty-ninth embodiment of the present application is a semiconductor manufacturing method for manufacturing a semiconductor using the apparatus of the fifty-fifth to fifty-eighth embodiments.

A fine semiconductor circuit can be formed by manufacturing a semiconductor with an apparatus in which the stage positioning performance is highly accurate and the degree of vacuum in the charged beam irradiation region is stable.
According to the embodiment of the present application No. 55-59, the following effects can be obtained.
(B) Using a stage having a structure similar to that of a static pressure bearing type stage generally used in the atmosphere (a stage supporting a static pressure bearing that does not have a differential pumping mechanism) Processing with a charged particle beam can be performed stably.
(B) It is possible to minimize the influence of the charged particle beam irradiation region on the degree of vacuum, and the processing of the charged particle beam on the sample can be stabilized.
(C) It is possible to provide an inspection apparatus with high accuracy in stage positioning performance and a stable vacuum degree in a charged particle beam irradiation area at low cost.
(D) It is possible to provide an exposure apparatus with high accuracy in positioning of the stage and a stable degree of vacuum in the charged particle beam irradiation area at low cost.
(E) A fine semiconductor circuit can be formed by manufacturing a semiconductor with an apparatus in which the stage positioning performance is highly accurate and the degree of vacuum in the charged particle beam irradiation region is stable.

In the inspection method for inspecting the inspection object by irradiating the inspection object with one of charged particles or electromagnetic waves,
A working chamber that can be controlled in a vacuum atmosphere and that inspects an inspection object;
Beam generating means for generating one of charged particles or electromagnetic waves as a beam;
An electron optical system that guides and irradiates the inspection target held in the working chamber, detects secondary charged particles generated from the inspection target, and guides the image to an image processing system;
An image processing system for forming an image with the secondary charged particles;
Based on the output of the image processing system, an information processing system that displays and / or stores state information of the inspection object;
A stage device that holds an inspection target so as to be movable relative to the beam;
By measuring the position of the inspection object, the beam is accurately positioned on the inspection object,
Deflect the beam to the desired position of the measured object to be measured;
Irradiating the desired position of the surface to be inspected with the beam,
Detecting secondary charged particles arising from the inspection object;
Forming an image with the secondary charged particles;
Based on the output of the image processing system, the state information of the inspection object is displayed and / or stored.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings as a semiconductor inspection apparatus for inspecting a substrate, ie, a wafer, on which a pattern is formed as an inspection object.

  1 and 2A, the main components of the semiconductor inspection apparatus 1 of the present embodiment are shown in an elevational plane and a plane.

The semiconductor inspection apparatus 1 according to the present embodiment includes a cassette holder 10 that holds a cassette that stores a plurality of wafers, a mini-environment device 20, a main housing 30 that defines a working chamber, and a mini-environment device 20. A loader housing 40 disposed between the main housing 30 and defining two loading chambers; a loader 60 for loading a wafer from the cassette holder 10 onto a stage device 50 disposed in the main housing 30; And an electro-optical device 70 attached to the vacuum housing, which are arranged in a positional relationship as shown in FIGS. 1 and 2A. The semiconductor inspection apparatus 1 further includes a precharge unit 81 disposed in the vacuum main housing 30, a potential applying mechanism 83 (shown in FIG. 29) for applying a potential to the wafer, and an electron beam calibration mechanism 85 (see FIG. 30) and an optical microscope 871 that constitutes an alignment control device 87 for positioning the wafer on the stage device.
Cassette holder The cassette holder 10 includes a plurality of cassettes c (for example, closed cassettes such as SMIF and FOUP manufactured by Assist) in which a plurality of wafers (for example, 25 wafers) are stored in a state of being arranged in parallel in the vertical direction. The number (two in this embodiment) is held. As this cassette holder, a cassette having a structure suitable for the case where the cassette is transported by a robot or the like and automatically loaded into the cassette holder 10, or an open cassette having a structure suitable for the manual loading is used. Each can be selected and installed. In this embodiment, the cassette holder 10 is a type in which the cassette c is automatically loaded. The cassette holder 10 includes, for example, an elevating table 11 and an elevating mechanism 12 that moves the elevating tail 11 up and down. The cassette c is on the elevating table. 2A can be automatically set in the state shown by the chain line in FIG. 2A, and after the setting, it is automatically rotated to the state shown in the solid line in FIG. 2A to rotate the first transport unit in the mini-environment device. Directed to the axis. Further, the lifting table 11 is lowered to the state shown by the chain line in FIG. As described above, the cassette holder used for automatic loading or the cassette holder used for manual loading may be a known structure as appropriate. Description is omitted.

  In another embodiment, as shown in FIG. 2B, a plurality of 300 mm substrates are accommodated in a grooved pocket (not shown) fixed inside the box body 501, and transported, stored, etc. It is. The substrate transport box 24 is connected to a rectangular tube-shaped box body 501 and a substrate loading / unloading door automatic opening / closing device, and a substrate loading / unloading door 502 capable of opening and closing a side opening of the box body 501 by a machine, A lid 503 that is positioned on the opposite side and covers an opening for attaching and detaching filters and a fan motor, a grooved pocket (not shown) for holding the substrate W, a ULPA filter 505, a chemical filter 506, And a fan motor 507. In this embodiment, the substrate is loaded and unloaded by the robot-type first transfer unit 612 of the loader 60.

The substrate, that is, the wafer housed in the cassette c is a wafer to be inspected, and such inspection is performed after or during the process of processing the wafer in the semiconductor manufacturing process. Specifically, a substrate that has been subjected to a film forming process, CMP, ion implantation, or the like, that is, a wafer having a wiring pattern formed on the surface, or a wafer on which a wiring pattern has not yet been formed is stored in a cassette. Since a large number of wafers accommodated in the cassette c are arranged side by side in parallel in the vertical direction, the first transfer unit can be held by the wafer at an arbitrary position and the first transfer unit described later. The arm can be moved up and down.
In the mini-environment apparatus FIGS. 1 to 3, the mini-environment apparatus 20 includes a housing 22 which defines a mini-environment space 21 adapted to be controlled atmosphere, the clean air within the mini-environment space 21 Such a gas circulation device 23 for circulating the gas to control the atmosphere, a discharge device 24 for collecting and discharging a part of the air supplied into the mini-environment space 21, and the mini-environment space 21 And a pre-aligner 25 for roughly positioning a substrate, that is, a wafer to be inspected.

  The housing 22 has a top wall 221, a bottom wall 222, and a peripheral wall 223 that surrounds the four circumferences, and has a structure that blocks the mini-environment space 21 from the outside. In order to control the atmosphere of the mini-environment space, the gas circulation device 23 is attached to the top wall 221 in the mini-environment space 21 as shown in FIG. 3, and gas (air in this embodiment) is installed. And a gas supply unit 231 for flowing clean air in a laminar flow downwardly through one or more gas outlets (not shown) and disposed on the bottom wall 222 in the mini-environment space A recovery duct 232 that recovers air that has flowed down toward the bottom, and a conduit 233 that connects the recovery duct 232 and the gas supply unit 231 and returns the recovered air to the gas supply unit 231. Yes. In this embodiment, the gas supply unit 231 takes in and cleans about 20% of the supplied air from the outside of the housing 22, but the ratio of the gas taken in from the outside can be arbitrarily selected. . The gas supply unit 231 includes a HEPA or ULPA filter having a known structure for producing clean air. The laminar flow of the clean air, that is, the downward flow, is mainly supplied to flow through the transfer surface of the first transfer unit, which will be described later, disposed in the mini-environment space 21, and is generated by the transfer unit. This prevents dust that may be adhered to the wafer. Therefore, it is not always necessary that the downflow jet outlet is located close to the top wall as shown in the drawing, and it is sufficient if it is above the transport surface of the transport unit. Moreover, there is no need to flow over the entire mini-environment space. In some cases, cleanliness can be ensured by using ion wind as clean air. Further, a sensor for observing the cleanliness can be provided in the mini-environment space, and the apparatus can be shut down when the cleanliness deteriorates. An entrance / exit 225 is formed in a portion of the peripheral wall 223 of the housing 22 adjacent to the cassette holder 10. A shutter device having a known structure may be provided near the entrance / exit 225 so that the entrance / exit 225 is closed from the mini-environment device side. The laminar flow downflow created near the wafer may be, for example, a flow rate of 0.3 to 0.4 m / sec. The gas supply unit may be provided outside the mini-environment space.

  The discharge device 24 includes a suction duct 241 disposed below the transfer unit at a position below the wafer transfer surface of the transfer unit, a blower 242 disposed outside the housing 22, a suction duct 241, and a blower 242. And a conduit 243 for connecting the two. The discharge device 24 sucks a gas containing dust that may flow around the transport unit and may be generated by the transport unit through the suction duct 241, and the outside of the housing 22 through the conduits 243 and 244 and the blower 242. To discharge. In this case, the air may be discharged into an exhaust pipe (not shown) drawn near the housing 22.

The aligner 25 disposed in the mini-environment space 21 is formed on the orientation flat (referred to as a flat portion formed on the outer periphery of a circular wafer, hereinafter referred to as an orientation flat) formed on the wafer, or on the outer peripheral edge of the wafer. One or more V-shaped notches or notches are detected optically or mechanically to pre-position the rotational position around the wafer axis OO with an accuracy of about ± 1 degree. It is supposed to keep. The pre-aligner constitutes a part of the mechanism for determining the coordinates of the inspection object according to the invention described in the claims, and is responsible for the rough positioning of the inspection object. Since this pre-aligner itself may have a known structure, description of its structure and operation is omitted.

Although not shown, a recovery duct for a discharge device may be provided below the pre-aligner so that air containing dust discharged from the pre-aligner is discharged to the outside.
In the main housing FIGS. 1 and 2, the main housing 30 which defines a working chamber 31 includes a housing body 32, the housing body 32, base frame 36 of the vibration isolation device or vibration isolator 37 is disposed on It is supported by a housing support device 33 placed thereon. The housing support device 33 includes a frame structure 331 assembled in a rectangular shape. The housing main body 32 is disposed and fixed on the frame structure 331, and is connected to the bottom wall 321 mounted on the frame structure, the top wall 322, the bottom wall 321 and the top wall 322, and surrounds the circumference. 323 to isolate the working chamber 31 from the outside. In this embodiment, the bottom wall 321 is composed of a relatively thick steel plate so as not to be distorted by weighting by a device such as a stage device mounted on the bottom wall 321. Good. In this embodiment, the housing body and the housing support device 33 are assembled in a rigid structure, and vibrations from the floor on which the base frame 36 is installed are prevented from being transmitted to the rigid structure by the vibration isolator 37. It is supposed to do. Of the peripheral wall 323 of the housing body 32, an entrance / exit 325 for taking in and out the wafer is formed in a peripheral wall adjacent to a loader housing described later.

The vibration isolator may be an active type having an air spring, a magnetic bearing or the like, or a passive type having these. Since any of them may have a known structure, description of its own structure and function is omitted. The working chamber 31 is maintained in a vacuum atmosphere by a known vacuum device (not shown). A control device 2 that controls the operation of the entire apparatus is disposed under the base frame 36.
Loader Housing Referring to FIGS. 1, 2, and 4, the loader housing 40 includes a housing body 43 that defines a first loading chamber 41 and a second loading chamber 42. The housing main body 43 includes a bottom wall 431, a top wall 432, a peripheral wall 433 that surrounds the four circumferences, and a partition wall 434 that partitions the first loading chamber 41 and the second loading chamber 42. Can be isolated from the outside. The partition wall 434 has an opening, that is, an entrance / exit 435 for exchanging wafers between both loading chambers. In addition, entrances 436 and 437 are formed in a portion of the peripheral wall 433 adjacent to the mini-environment device and the main housing. The housing main body 43 of the loader housing 40 is placed on and supported by the frame structure 331 of the housing support device 33. Therefore, the floor vibration is not transmitted to the loader housing 40. A shutter device for selectively preventing communication between the mini-environment space 21 and the first loading chamber 41 is aligned with the entrance / exit 436 of the loader housing 40 and the entrance / exit 226 of the housing 22 of the mini-environment device. 27 is provided. The shutter device 27 surrounds the doorways 226 and 436 and seals 271 fixed in close contact with the side wall 433, and a door 272 that blocks air flow through the doorway in cooperation with the sealant 271. And a driving device 273 for moving the door. Further, the entrance / exit 437 of the loader housing 40 and the entrance / exit 325 of the housing main body 32 are aligned with each other, and there is a shutter device 45 that selectively blocks the communication between the second loading chamber 42 and the working chamber 31. Is provided. The shutter device 45 surrounds the entrances and exits 437 and 325, closely contacts the side walls 433 and 323, and cooperates with the sealing material 451 and the sealing material 451 that are fixed to the side walls 433 and 323. It has a door 452 for blocking and a driving device 453 for moving the door. Further, the opening formed in the partition wall 434 is provided with a shutter device 46 which is closed by a door 461 and selectively prevents communication between the first and second loading chambers. These shutter devices 27, 45 and 46 are adapted to hermetically seal each chamber when in the closed state. Since these shutter devices may be known ones, detailed description of their structure and operation will be omitted. The support method of the housing 22 of the mini-environment device 20 and the support method of the loader housing are different, and in order to prevent vibration from the floor from being transmitted to the loader housing 40 and the main housing 30 via the mini-environment device. In addition, an anti-vibration cushion material may be disposed between the housing 22 and the loader housing 40 so as to airtightly surround the doorway.

  In the first loading chamber 41, a wafer rack 47 is disposed that supports a plurality (two in this embodiment) of wafers in a horizontal state with a vertical separation. As shown in FIG. 5, the wafer rack 47 includes support columns 472 that are fixed upright at four corners of a rectangular substrate 471, and each support column 472 is formed with two-stage support portions 473 and 474. Then, the periphery of the wafer W is placed on and held on the support portion. Then, the tips of arms of first and second transfer units, which will be described later, are brought close to the wafer from between adjacent columns, and the wafer is held by the arm.

The loading chambers 41 and 42 can be controlled in an atmosphere to a high vacuum state (the degree of vacuum is 10 ⁻⁵ to 10 ⁻⁶ Pa) by a well-known vacuum exhaust device (not shown) including a vacuum pump (not shown). It has become. In this case, the first loading chamber 41 can be maintained as a low vacuum chamber in a low vacuum atmosphere, and the second loading chamber 42 can be maintained as a high vacuum chamber in a high vacuum atmosphere to effectively prevent wafer contamination. By adopting such a structure, a wafer which is accommodated in the loading chamber and to be inspected next can be transferred into the working chamber without delay. By adopting such a loading chamber, the throughput of defect inspection is improved together with the multi-beam electronic device principle described later, and the degree of vacuum around the electron source that is required to be kept in a high vacuum state is further increased. The vacuum can be as high as possible.

  The first and second loading chambers 41 and 42 are connected to a vacuum exhaust pipe and a vent pipe (not shown) for an inert gas (for example, dry pure nitrogen), respectively. Thereby, the atmospheric pressure state in each loading chamber is achieved by an inert gas vent (injecting an inert gas to prevent oxygen gas other than the inert gas from adhering to the surface). Since the apparatus for performing such an inert gas vent itself may have a known structure, a detailed description thereof will be omitted.

In the inspection apparatus of the present invention using an electron beam, a typical lanthanum hexaboride (LaB ₆ ) used as an electron source of an electron optical system to be described later is once brought into a high temperature state to the extent that thermal electrons are emitted. In the case of heating, it is important not to contact oxygen as much as possible in order not to shorten the lifetime, but as described above in the stage before carrying the wafer into the working chamber in which the electron optical system is arranged. It is possible to execute more reliably by performing a proper atmosphere control.

The stage apparatus 50 includes a fixed table 51 disposed on the bottom wall 321 of the main housing 30, a Y table 52 that moves in the Y direction (direction perpendicular to the paper surface in FIG. 1) on the fixed table, and a Y table. An X table 53 that moves upward in the X direction (left and right in FIG. 1), a rotary table 54 that can rotate on the X table, and a holder 55 that is arranged on the rotary table 54 are provided. The wafer is releasably held on the wafer placement surface 551 of the holder 55. The holder may have a known structure capable of releasably gripping the wafer mechanically or by an electrostatic chuck method. The stage apparatus 50 uses a servo motor, an encoder, and various sensors (not shown) to operate the plurality of tables as described above, thereby causing the wafer held by the holder on the mounting surface 551 to be electro-optically. It can be positioned with high accuracy in the X direction, Y direction, and Z direction (up and down direction in FIG. 1) with respect to the electron beam irradiated from the apparatus, and further in the direction around the vertical axis (θ direction) on the wafer support surface. It has become. For positioning in the Z direction, for example, the position of the mounting surface on the holder may be finely adjusted in the Z direction. In this case, the reference position of the mounting surface is detected by a position measuring device (laser interference distance measuring device using the principle of an interferometer) using a fine-diameter laser, and the position is controlled by a feedback circuit (not shown). Instead, the position of the notch or orientation flat of the wafer is measured to detect the planar position and rotation position of the wafer with respect to the electron beam, and the rotation table is rotated by a stepping motor capable of controlling a minute angle. In order to prevent the generation of dust in the working chamber as much as possible, the servomotors 521 and 531 for the stage device and the encoders 522 and 532 are arranged outside the main housing 30. Note that the stage device 50 may have a known structure used in, for example, a stepper or the like, and therefore a detailed description of the structure and operation thereof will be omitted. Further, since the laser interference distance measuring device may also have a known structure, detailed description of its structure and operation will be omitted.

  It is also possible to standardize a signal obtained by inputting the rotation position of the wafer with respect to the electron beam and the X and Y positions in advance to a signal detection system or an image processing system described later. Further, the wafer chuck mechanism provided in the holder is adapted to apply a voltage for chucking the wafer to the electrode of the electrostatic chuck, and has three points (preferably equally spaced in the circumferential direction) on the outer periphery of the wafer. It is designed to press and hold (separated). The wafer chuck mechanism includes two fixed positioning pins and one pressing crank pin. The clamp pin can realize automatic chucking and automatic release, and constitutes a conduction point for voltage application.

In this embodiment, the table that moves in the horizontal direction in FIG. 2 is the X table and the table that moves in the vertical direction is the Y table. However, the table that moves in the horizontal direction in FIG. The moving table may be an X table.
The loader loader 60 includes a robot-type first transport unit 61 disposed in the housing 22 of the mini-environment device 20, and a robot-type second transport unit 63 disposed in the second loading chamber 42. It has.

The first transport unit 61 includes a multi-node arm 612 that can rotate about the axis O ₁ -O ₁ with respect to the drive unit 611. As the multi-node arm, an arbitrary structure can be used, but in this embodiment, the multi-node arm has three portions which are rotatably attached to each other. One portion of the arm 612 of the first transport unit 61, that is, the first portion closest to the drive unit 611 is a shaft that can be rotated by a drive mechanism (not shown) having a known structure provided in the drive unit 611. 613 is attached. The arm 612 can be rotated around the axis O ₁ -O ₁ by the shaft 613 and can be expanded and contracted in the radial direction with respect to the axis O ₁ -O ₁ as a whole by relative rotation between the parts. A gripping device 616 for gripping a wafer such as a mechanical chuck or an electrostatic chuck having a known structure is provided at the tip of the third portion farthest from the shaft 613 of the arm 612. The drive unit 611 can be moved in the vertical direction by an elevating mechanism 615 having a known structure.

  In the first transfer unit 61, the arm extends in one direction M1 or M2 of the two cassettes c in which the arm 612 is held by the cassette holder, and one wafer is stored in the cassette c. The sample is placed on the arm or grasped by a chuck (not shown) attached to the tip of the arm and taken out. Thereafter, the arm contracts (as shown in FIG. 2), and the arm rotates to a position where it can extend in the direction M3 of the pre-aligner 25 and stops at that position. Then, the arm extends again and the wafer held by the arm is placed on the pre-aligner 25. After receiving the wafer from the pre-aligner in the opposite direction, the arm further rotates and stops at a position where it can extend toward the second loading chamber 41 (direction M4), and the wafer receiver 47 in the second loading chamber 41 is reached. Deliver the wafer. When the wafer is mechanically gripped, the peripheral edge of the wafer (in the range of about 5 mm from the peripheral edge) is gripped. This is because a device (circuit wiring) is formed on the entire surface of the wafer except for the peripheral portion, and if this portion is gripped, the device is broken or a defect is generated.

  The second transfer unit 63 is basically the same in structure as the first transfer unit, and is different only in that the wafer is transferred between the wafer rack 47 and the mounting surface of the stage apparatus. Therefore, detailed description is omitted.

In the loader 60, the first and second transfer units 61 and 63 transfer the wafer from the cassette held in the cassette holder onto the stage device 50 disposed in the working chamber 31 and vice versa. The arm of the transfer unit is moved up and down while maintaining the state. The wafer unit is simply taken out from the cassette and inserted into the cassette, placed on the wafer rack and taken out from the wafer rack, and the wafer stage device. It is only necessary to place it on and take it out of it. Therefore, a large wafer, for example, a wafer having a diameter of 30 cm can be moved smoothly.
Wafer Transfer Next , the transfer of the wafer from the cassette c supported by the cassette holder to the stage device 50 arranged in the working chamber 31 will be described in order.

  As described above, the cassette holder 10 has a structure suitable for manually setting a cassette, and a cassette holder 10 having a structure suitable for automatically setting a cassette. In this embodiment, when the cassette c is set on the lifting table 11 of the cassette holder 10, the lifting table 11 is lowered by the lifting mechanism 12 and the cassette c is aligned with the entrance / exit 225.

  When the cassette is aligned with the entrance / exit 225, a cover (not shown) provided on the cassette is opened, and a cylindrical cover is disposed between the cassette c and the entrance / exit 225 of the mini-environment so that the inside of the cassette and the mini-port Block the environment space from the outside. Since these structures are publicly known, detailed description of the structure and operation is omitted. When a shutter device that opens and closes the entrance / exit 225 is provided on the mini-environment device 20 side, the shutter device operates to open the entrance / exit 225.

  On the other hand, the arm 612 of the first transport unit 61 is stopped in a state facing the direction M1 or M2 (in this description, the direction of M1), and when the doorway 225 is opened, the arm extends and enters the cassette at the tip. One of the stored wafers is received. In this embodiment, the vertical position adjustment between the arm and the wafer to be taken out from the cassette is performed by the vertical movement of the driving unit 611 and the arm 612 of the first transfer unit 61. It may be performed up and down or both.

When the reception of the wafer by the arm 612 is completed, the arm contracts, the shutter device is operated to close the entrance / exit (when the shutter device is present), and then the arm 612 is rotated around the axis O ₁ -O ₁ in the direction. It will be in the state where it can extend toward M3. Then, the arm extends and is placed on the front end or the wafer held by the chuck is placed on the pre-aligner 25, and the orientation of the wafer in the rotation direction (direction around the central axis perpendicular to the wafer plane) is set by the pre-aligner. Position within a predetermined range. When the positioning is completed, the transfer unit 61 receives the wafer from the pre-aligner 25 at the tip of the arm and then contracts the arm so that the arm can be extended in the direction M4. Then, the door 272 of the shutter device 27 moves to open the entrances 226 and 436 and the arm 612 extends to place the wafer on the upper stage side or the lower stage side of the wafer rack 47 in the first loading chamber 41. Note that the opening 435 formed in the partition wall 434 is closed in an airtight state by the door 461 of the shutter device 46 before the shutter device 27 is opened and the wafer is transferred to the wafer rack 47 as described above.

  In the wafer transfer process by the first transfer unit, clean air flows in a laminar flow (as a downflow) from the gas supply unit 231 provided on the housing of the mini-environment device, and dust is generated during transfer. Prevents adhesion to the upper surface of the wafer. A part of the air around the transport unit (in this embodiment, air mainly contaminated with about 20% of the air supplied from the supply unit) is sucked from the suction duct 241 of the discharge device 24 and discharged out of the housing. The remaining air is recovered via a recovery duct 232 provided at the bottom of the housing and returned to the gas supply unit 231 again.

  When a wafer is loaded on the wafer rack 47 in the first loading chamber 41 of the loader housing 40 by the first transfer unit 61, the shutter device 27 is closed and the loading chamber 41 is sealed. Then, after the inert gas is expelled in the first loading chamber 41 and the air is expelled, the inert gas is also discharged and the inside of the loading chamber 41 is made a vacuum atmosphere. The vacuum atmosphere of the first loading chamber may be a low vacuum level. When the degree of vacuum in the loading chamber 41 is obtained to some extent, the shutter device 46 operates to open the doorway 434 that has been sealed by the door 461, the arm 632 of the second transfer unit 63 extends, and the wafer is held by the gripping device at the tip. One wafer is received from the receiver 47 (mounted on the tip or held by a chuck attached to the tip). When the receipt of the wafer is completed, the arm contracts, and the shutter device 46 operates again to close the doorway 435 with the door 461. Note that before the shutter device 46 is opened, the arm 632 can be extended in advance in the direction N1 of the wafer rack 47. In addition, as described above, the doors 437 and 325 are closed by the door 452 of the shutter device 45 before the shutter device 46 is opened, thereby preventing communication between the second loading chamber 42 and the working chamber 31 in an airtight state. The inside of the second loading chamber 42 is evacuated.

When the shutter device 46 closes the entrance / exit 435, the inside of the second loading chamber is evacuated again, and is evacuated at a higher degree of vacuum than in the first loading chamber. Meanwhile, the arm of the second transfer unit 61 is rotated to a position where it can extend toward the stage device 50 in the working chamber 31. Meanwhile the stage apparatus in the working chamber 31, Y table 52, the center line _X 0 -X ₀ X-axis _X 1 -X through the rotation axis _O 2 -O ₂ of the second transfer unit 63 of the X table 53 ₁ and to approximately match the position, moves upward in FIG. 2, Further, X table 53 is moved to a position close to the leftmost position in FIG. 2, is waiting in this state. When the second loading chamber becomes substantially the same as the vacuum state of the working chamber, the door 452 of the shutter device 45 moves to open the entrances 437 and 325, and the tip of the arm that holds the wafer by extending the arm is in the working chamber 31. Approach the stage device. Then, a wafer is placed on the placement surface 551 of the stage apparatus 50. When the placement of the wafer is completed, the arm contracts and the shutter device 45 closes the entrances 437 and 325.

  The above is the description of the operation until the wafer in the cassette c is transferred onto the stage device. Perform the operation and return. Further, since a plurality of wafers are placed on the wafer rack 47, the cassette and the wafer rack are used in the first transfer unit while the wafer is transferred between the wafer rack and the stage apparatus in the second transfer unit. The wafer can be transferred between the two and the inspection process can be performed efficiently.

Specifically, when there are already processed wafers A and unprocessed wafers B in the wafer rack 47 of the second transfer unit,
First, the unprocessed wafer B is moved to the stage apparatus 50, and the processing is started.

  During this processing, the processed wafer A is moved from the stage device 50 to the wafer rack 47 by the arm, and the unprocessed wafer C is extracted from the wafer rack by the arm and positioned by the pre-aligner, and then the wafer in the loading chamber 41 Move to rack 47.

      In this way, in the wafer rack 47, the processed wafer A can be replaced with the unprocessed wafer C while the wafer B is being processed.

    Further, depending on how to use such an apparatus for performing inspection and evaluation, a plurality of stage apparatuses 50 are placed in parallel, and a plurality of wafers can be transferred by moving wafers from one wafer rack 47 to each apparatus. The same processing can be performed.

  FIG. 6 shows a modification of the method for supporting the main housing. In the modification shown in FIG. 6, the housing support device 33a is formed of a thick and rectangular steel plate 331a, and the housing body 32a is placed on the steel plate. Therefore, the bottom wall 321a of the housing body 32a has a thin structure as compared with the bottom wall of the above embodiment. In the modification shown in FIG. 7, the housing body 32b and the loader housing 40b are suspended and supported by the frame structure 336b of the housing support device 33b. Lower ends of the plurality of vertical frames 337b fixed to the frame structure 336b are fixed to four corners of the bottom wall 321b of the housing main body 32b, and the peripheral wall and the top wall are supported by the bottom walls. The vibration isolator 37b is disposed between the frame structure 336b and the base frame 36b. The loader housing 40 is also suspended by a suspension member 49b fixed to the frame structure 336. In the modification shown in FIG. 7 of the housing main body 32b, since it is supported in a suspended manner, the center of gravity of the main housing and the various devices provided therein can be lowered. In the main housing and loader housing support methods including the above-described modifications, vibrations from the floor are not transmitted to the main housing and the loader housing.

  In another variant not shown, only the main housing exterior of the main housing is supported from below by the housing support device, and the loader housing can be placed on the floor in the same way as the adjacent mini-environment device. In yet another variant, not shown, only the housing body of the main housing is supported in a suspended manner on the frame structure, and the loader housing can be placed on the floor in the same manner as the adjacent mini-environment device.

According to the above embodiment, the following effects can be obtained.
(A) The entire configuration of a mapping projection type inspection apparatus using an electron beam is obtained, and an inspection object can be processed with high throughput.
(B) Inspecting the inspection object while monitoring the dust in the space by providing a sensor for preventing the adhesion of dust by flowing clean gas to the inspection object in the mini-environment space and observing the cleanliness. Can do.
(C) Since the loading chamber and the working chamber are integrally supported via the vibration preventing device, it is possible to supply and inspect the inspection target to the stage device without being affected by the external environment.

Electron Optical Device The electron optical device 70 includes a lens barrel 71 fixed to the housing body 32, and includes a primary electron optical system (hereinafter simply referred to as a primary optical system) 72 as schematically illustrated in FIG. An electron optical system including a secondary electron optical system (hereinafter simply referred to as a secondary optical system) 74 and a detection system 76 are provided. The primary optical system 72 is an optical system that irradiates the surface of the wafer W to be inspected with an electron beam, and an electron gun 721 that emits an electron beam and an electrostatic lens that focuses the primary electron beam emitted from the electron gun 721. , A Wien filter, ie, an E × B separator 723, and an objective lens system 724, which are arranged in order with the electron gun 721 at the top as shown in FIG. . The lens constituting the objective lens system 724 of this embodiment is a deceleration electric field type objective lens. In this embodiment, the optical axis of the primary electron beam emitted from the electron gun 721 is oblique with respect to the irradiation optical axis (perpendicular to the wafer surface) irradiated to the wafer W to be inspected. . An electrode 725 is disposed between the objective lens system 724 and the wafer W to be inspected. The electrode 725 has an axisymmetric shape with respect to the irradiation optical axis of the primary electron beam, and the voltage is controlled by a power source 726.

  The secondary optical system 74 includes a lens system 741 including an electrostatic lens that passes secondary electrons separated from the primary optical system by the E × B deflector 724. This lens system 741 functions as a magnifying lens that magnifies the secondary electron image.

The detection system 76 includes a detector 761 and an image processing unit 763 arranged on the image plane of the lens system 741.

Electron gun (electron beam source)
A thermal electron beam source is used as the electron beam source. The electron emission (emitter) material is L _a B ₆ . Other materials can be used as long as the material has a high melting point (low vapor pressure at high temperature) and a small work function. A cone-shaped tip or a truncated cone shape with the cone tip cut off is used. The diameter of the tip of the truncated cone is about 100 μm. As another method, a field emission type electron beam source or a thermal field emission type is used, but a relatively wide area (for example, 100 × 25 to 400 × 100 μm ² ) is large as in the present invention. When irradiating with current (about 1 μA), a thermoelectron source using L _a B ₆ is optimal. (The SEM method generally uses a thermal field electron beam source). The thermionic beam source is a method in which electrons are emitted by heating the electron emission material. The thermal field emission electron beam source is an electron beam emitted by applying a high electric field to the electron emission material. This is a system in which electron emission is stabilized by heating the emission part.
The electron beam irradiated from the primary electron optical system electron gun is formed, and the portion that irradiates a rectangular or circular (elliptical) electron beam on the wafer surface is called a primary electron optical system. The beam size and current density can be controlled by controlling the lens conditions of the primary electron optical system. Further, the primary electron beam is vertically incident on the wafer by an E × B (Wien filter) filter of the primary / secondary electron optical system connecting portion.

The L _a B ₆ heat electrons emitted from the cathode, Wehnelt and forms a crossover image on stop cancer triple anode lens. An electron beam whose angle of incidence on the lens is optimized by the illumination field stop is controlled to form an image on the NA stop in a rotationally asymmetric manner by controlling the primary electrostatic lens, and then irradiated onto the wafer surface. The subsequent stage of the primary electrostatic lens is composed of a three-stage quadrupole (QL) and a single-stage aperture aberration correcting electrode. Although the quadrupole lens has a limitation that alignment accuracy is severe, it has a characteristic that it has a stronger convergence effect than a rotationally symmetric lens, and an aperture aberration equivalent to the spherical aberration of the rotationally symmetric lens is applied to the aperture aberration correction electrode. Then, correction can be performed. Thereby, a uniform surface beam can be irradiated to a predetermined area.
Secondary electron optical system A two-dimensional secondary electron image generated by an electron beam irradiated on the wafer is imaged at a field stop position by an electrostatic lens (CL, TL) corresponding to an objective lens. Magnify and project at PL). This imaging projection optical system is called a secondary electron optical system.

  At this time, a negative bias voltage (deceleration electric field voltage) is applied to the wafer. The decelerating electric field has a decelerating effect on the irradiation beam, reduces sample damage, and accelerates secondary electrons generated from the sample surface due to the potential difference between CL and the wafer, thereby reducing chromatic aberration. The electrons converged by CL are imaged on FA by TL, the image is enlarged and projected by PL, and imaged on a secondary electron detector (MCP). In this optical system, an NA is arranged between the CL and TL, and an optical system capable of reducing off-axis aberrations is configured by optimizing the NA.

In addition, an electrostatic octupole (STIG) is used to correct the manufacturing error of the electron optical system and the astigmatism and anisotropic magnification of the image generated by passing through the E × B filter (Wien filter). Arrangement is performed and correction is made, and correction for axial deviation is performed by a deflector (OP) arranged between the lenses. As a result, a mapping optical system with a uniform resolution in the field of view can be achieved.
E × B unit (Vienna filter)
This is an electromagnetic prism optical system unit in which electrodes and magnetic poles are arranged in an orthogonal direction, and an electric field and a magnetic field are orthogonalized. When an electromagnetic field is selectively applied, the electron beam incident on the field from one direction is deflected, and the electron beam incident from the opposite direction is a condition that cancels the influence of the force received from the electric field and the force from the magnetic field ( Wien condition) can be created, whereby the primary electron beam is deflected and radiates vertically onto the wafer, and the secondary electron beam can travel straight towards the detector.

  The detailed structure of the electron beam deflecting unit 723 will be described with reference to FIG. 9 and FIG. 10 showing a longitudinal section along the line AA in FIG. As shown in FIG. 9, the field of the electron beam deflecting unit has a structure in which an electric field and a magnetic field are orthogonal to each other in a plane perpendicular to the optical axis of the mapping projection optical unit, that is, an E × B structure.

Here, the electric field is generated by the electrodes 723-1 and 723-2 having concave curved surfaces. The electric fields generated by the electrodes 723-1 and 723-2 are controlled by the control units 723a and 723d, respectively. On the other hand, a magnetic field is generated by arranging electromagnetic coils 723-1 a and 723-2 a so as to be orthogonal to the electric field generating electrodes 723-1 and 723-2. Note that the electrodes 723-1 and 723-2 for generating electrolysis are point targets. (Concentric circles are also acceptable.)
In this case, in order to improve the uniformity of the magnetic field, the magnetic path 42 is formed by providing a pole piece having a parallel plate shape. The behavior of the electron beam in the longitudinal section along the AA line is as shown in FIG. The irradiated electron beams 711a and 711b are deflected by the electric field generated by the electrodes 723-1 and 723-2 and the magnetic field generated by the electromagnetic coils 723-1a and 723-2a, and are then directed onto the sample surface. Incident in the vertical direction.

Here, the incident positions and angles of the irradiated electron beams 711a and 711b to the electron beam deflecting unit 723 are uniquely determined when the energy of electrons is determined. Further, the conditions of the electric field and magnetic field, that is, the electric field generated by the electrodes 723-1 and 723-2 so that vB = E, and the electromagnetic coils 723-1 a and 723-so that the secondary electrons 712 a and 712 b travel straight ahead. The control units 723a and 723d, 723c and 723b control the magnetic field generated by 2a, so that the secondary electrons travel straight through the electron beam deflecting unit 723 and enter the mapping projection optical unit. Here, V is the velocity (m / s) of the electron 712, B is the magnetic field (T), e is the charge amount (C), and E is the electric field (V / m).
A secondary electron image from the wafer imaged by the detector secondary optical system is first amplified by a microchannel plate (MCP) and then converted to an image of light by hitting a fluorescent screen. The principle of MCP is a bundle of millions of very thin conductive glass capillaries with a diameter of 6 to 25 μm and a length of 0.24 to 1.0 mm, which are shaped into a thin plate and applied with a predetermined voltage. Thus, each capillary serves as an independent secondary electron amplifier, and forms a secondary electron amplifier as a whole.

  The image converted into light by this detector is projected one-to-one on the TDI-CCD by the FOP system placed in the atmosphere through the vacuum transmission window.

  Next, the operation of the electron optical device 70 having the above configuration will be described.

  As shown in FIG. 8, the primary electron beam emitted from the electron gun 721 is focused by the lens system 722. The converged primary electron beam is incident on an E × B type deflector 723, deflected so as to irradiate the surface of the wafer W perpendicularly, and imaged on the surface of the wafer W by the objective lens system 724.

  The secondary electrons emitted from the wafer by the irradiation of the primary electron beam are accelerated by the objective lens system 724, enter the E × B type deflector 723, go straight through the deflector, and enter the lens system 741 of the secondary optical system. To the detector 761. Then, it is detected by the detector 761, and the detection signal is sent to the image processing unit 763.

  In this embodiment, it is assumed that the objective lens system 724 is applied with a high voltage of 10 to 20 kV and the wafer is installed.

  Here, when the wafer W has a via b and the voltage applied to the electrode 725 is −200 V, the electric field on the electron beam irradiation surface of the wafer is 0 to −0.1 V / mm (− is the high potential on the wafer W side). It shows that). In this state, no discharge is generated between the objective lens system 724 and the wafer W, and the defect inspection of the wafer W can be performed, but the detection efficiency of secondary electrons is slightly lowered. Accordingly, a series of operations for irradiating an electron beam and detecting secondary electrons is performed, for example, four times, and the detection results obtained for four times are subjected to processing such as cumulative addition and averaging to obtain a predetermined detection sensitivity. .

Further, even when the voltage applied to the electrode 725 is +350 V when the wafer does not have the via b, the wafer W can be inspected for defects without causing discharge between the objective lens system 724 and the wafer. In this case, the secondary electrons are focused by the voltage applied to the electrode 725 and further focused by the objective lens 724, so that the detection efficiency of the secondary electrons in the detector 761 is improved. Therefore, the processing as a wafer defect apparatus is also performed at high speed, and inspection can be performed with high throughput.

Relationship of Main Functions of Mapping Projection Method and Description of Overall Image FIG. 11 shows an overall configuration diagram of the present embodiment. However, a part of the configuration is omitted.

  In FIG. 11, the inspection apparatus has a primary column 71-1, a secondary column 71-2 and a chamber 32. An electron gun 721 is provided inside the primary column 71-1, and the primary optical system 72 is disposed on the optical axis of the electron beam (primary beam) emitted from the electron gun 721. A stage 50 is installed inside the chamber 32, and the sample W is placed on the stage 50.

  On the other hand, in the secondary column 71-2, on the optical axis of the secondary beam generated from the sample W, the cathode lens 724, the numerical aperture NA-2, the Wien filter 723, the second lens 741-1, the field An aperture NA-3, a third lens 741-2, a fourth lens 741-3, and a detector 761 are disposed. The numerical aperture NA-2 corresponds to an aperture stop, and is a metal (Mo or the like) thin plate with a circular hole. The aperture is arranged so as to be the primary beam focusing position and the focal position of the cathode lens 724. Therefore, the cathode lens 724 and the numerical aperture NA-2 constitute a telecentric electron optical system.

  On the other hand, the output of the detector 761 is input to the control unit 780, and the output of the control unit 780 is input to the CPU 781. The control signal of the CPU 781 is input to the primary column control unit 71a, the secondary column control unit 71b, and the stage drive mechanism 56. The primary column control unit 71a controls the lens voltage of the primary optical system 72, and the secondary column control unit 71b controls the lens voltage of the cathode lens 724, the second lens 741-1 to the fourth lens 741-3 and the Wien filter. The electromagnetic field applied to 723 is controlled.

The stage driving mechanism 56 transmits stage position information to the CPU 781. Further, the primary column 71-1, the secondary column 71-2, and the chamber 32 are connected to an evacuation system (not shown), and are evacuated by a turbo pump of the evacuation system, and the inside is maintained in a vacuum state. Yes.
(Primary Beam) The primary beam from the electron gun 721 is incident on the Wien filter 723 while receiving a lens action by the primary optical system 72. Here, as the tip of the electron gun, L _a B ₆ that can extract a large current with a rectangular cathode is used. The primary optical system 72 uses a rotation axis asymmetric quadrupole or octupole electrostatic (or electromagnetic) lens. This can cause convergence and divergence in the X-axis and Y-axis as in the so-called cylindrical lens. This lens is composed of two stages and three stages, and by optimizing each lens condition, the beam irradiation area on the sample surface is shaped into an arbitrary rectangular or elliptical shape without losing irradiation electrons. be able to.

  Specifically, when an electrostatic lens is used, four cylindrical rods are used. Opposing electrodes are equipotential, and opposite voltage characteristics are given.

  In addition, as a quadrupole lens, a lens having a shape obtained by dividing a generally used circular plate into four by an electrostatic deflector may be used instead of a cylindrical shape. In this case, the lens can be reduced in size. The primary beam that has passed through the primary optical system 72 has its trajectory bent by the deflection action of the Wien filter 723. The Wien filter 723, when the magnetic field and the electric field are orthogonal to each other, when the electric field is E, the magnetic field is B, and the velocity of the charged particles is v, only the charged particles satisfying the Wien condition of E = vB travel straight. Bend the trajectory. For the primary beam, a force FB caused by a magnetic field and a force FE caused by an electric field are generated, and the beam trajectory is bent. On the other hand, for the secondary beam, since the force FB and force FE work in opposite directions, they cancel each other, so the secondary beam goes straight.

  The lens voltage of the primary optical system 72 is set in advance so that the primary beam forms an image at the opening of the numerical aperture NA-2. This numerical aperture NA-2 prevents an extra electron beam scattered in the apparatus from reaching the sample surface and prevents charge-up and contamination of the sample W. Furthermore, since the numerical aperture NA-2 and the cathode lens 724 constitute a telecentric electron optical system, the primary beam transmitted through the cathode lens 724 becomes a parallel beam, and irradiates the sample W uniformly and uniformly. . That is, Koehler illumination referred to as an optical microscope is realized.

  (Secondary beam) When the sample is irradiated with the primary beam, secondary electrons, reflected electrons or backscattered electrons are generated as a secondary beam from the beam irradiation surface of the sample.

  The secondary beam passes through the lens while receiving the lens action of the cathode lens 724.

  Incidentally, the cathode lens 724 is composed of three electrodes. The bottom electrode is designed to form a positive electric field with the potential on the sample W side, draw electrons (especially secondary electrons with small directivity), and efficiently guide them into the lens. Yes.

  The lens action is performed by applying a voltage to the first and second electrodes of the cathode lens 724 to bring the third electrode to zero potential. On the other hand, the numerical aperture NA-2 is disposed at the focal position of the cathode lens 724, that is, the back focus position from the sample W. Therefore, the light beam of the electron beam emitted from the center of the field of view (off-axis) also becomes a parallel beam and passes through the center position of the numerical aperture NA-2 without being distorted.

  The numerical aperture NA-2 plays a role of suppressing the lens aberration of the second lens 741-1 to the fourth lens 741-3 for the secondary beam. The secondary beam that has passed through the numerical aperture NA-2 travels straight without passing through the deflection action of the Wien filter 723. Note that by changing the electromagnetic field applied to the Wien filter 723, only electrons having specific energy (for example, secondary electrons, reflected electrons, or backscattered electrons) are guided to the detector 761 from the secondary beam. it can.

  When the secondary beam is imaged only by the cathode lens 724, the lens action becomes strong and aberration is likely to occur. Therefore, one image formation is performed together with the second lens 741-1. The secondary beam obtains an intermediate image on the field aperture NA-3 by the cathode lens 724 and the second lens 741-1. In this case, normally, the magnification necessary for the secondary optical system is often insufficient, and therefore a configuration in which a third lens 741-2 and a fourth lens 741-3 are added as lenses for enlarging the intermediate image. To. The secondary beam is enlarged and imaged by the third lens 741-2 and the fourth lens 741-3, respectively, and is imaged three times in total here. The third lens 741-2 and the fourth lens 741-3 may be combined and imaged once (total twice).

  Further, the second lens 741-1 to the fourth lens 741-3 are all rotational axis symmetric lenses called unipotential lenses or Einzel lenses. Each lens has a configuration of three electrodes. Usually, the outer two electrodes are set to zero potential, and the lens action is performed with a voltage applied to the center electrode. Further, a field aperture NA-3 is arranged at the intermediate image formation point. The field aperture NA-3 limits the field of view to the necessary range, similar to the field stop of the optical microscope. However, in the case of an electron beam, an extra beam is passed through the third lens 741-2 and the fourth lens 741- at the subsequent stage. 3 to prevent the detector 761 from being charged up or contaminated. The enlargement magnification is set by changing the lens condition (focal length) of the third lens 741-2 and the fourth lens 741-3.

  The secondary beam is enlarged and projected by the secondary optical system, and forms an image on the detection surface of the detector 761. The detector 761 includes an MCP that amplifies electrons, a fluorescent plate that converts electrons into light, a relay between the vacuum system and the outside, and a lens and other optical elements for transmitting an optical image, and an image sensor (CCD or the like). It consists of. The secondary beam forms an image on the MCP detection surface and is amplified, and the electrons are converted into an optical signal by the fluorescent plate and converted into a photoelectric signal by the imaging device.

  The control unit 780 reads the image signal of the sample from the detector 761 and transmits it to the CPU 781. The CPU 781 performs a pattern defect inspection from the image signal by template matching or the like. The stage 50 can be moved in the XY directions by a stage driving mechanism 56. The CPU 781 reads the position of the stage 50, outputs a drive control signal to the stage drive mechanism 56, drives the stage 50, and sequentially detects and inspects images.

  As described above, in the inspection apparatus according to the present embodiment, the numerical aperture NA-2 and the cathode lens 724 constitute a telecentric electron optical system. Therefore, for the primary beam, the beam is made uniform on the sample. Can be irradiated. That is, Kohler illumination can be easily realized.

  Further, for the secondary beam, all the principal rays from the sample W are incident on the cathode lens 724 perpendicularly (parallel to the lens optical axis) and pass through the numerical aperture NA-2, so that the ambient light is also generated. The image brightness at the periphery of the sample does not decrease. In addition, a so-called lateral chromatic aberration occurs in which the imaging position differs depending on the energy variation of the electrons (particularly, secondary electrons have a large lateral chromatic aberration due to large energy variation), but the focal position of the cathode lens 724 In addition, the chromatic aberration of magnification can be suppressed by arranging the numerical aperture NA-2.

  Further, since the enlargement magnification is changed after passing through the numerical aperture NA-2, the field of view on the detection side can be changed even if the setting magnification of the lens conditions of the third lens 741-2 and the fourth lens 741-3 is changed. A uniform image can be obtained on the entire surface. In the present embodiment, a uniform image without unevenness can be acquired. However, usually, when the enlargement magnification is increased, the brightness of the image is lowered. Therefore, in order to improve this, when changing the magnification condition by changing the lens conditions of the secondary optical system, the effective field of view on the sample surface determined accordingly, and the electron beam irradiated on the sample surface, The lens conditions of the primary optical system are set so that they have the same size.

  In other words, if the magnification is increased, the field of view is narrowed accordingly, but at the same time, by increasing the irradiation energy density of the electron beam, the signal density of the detected electrons can be increased even if it is enlarged and projected by the secondary optical system. It is always kept constant and the brightness of the image does not decrease.

In the inspection apparatus of the present embodiment, the Wien filter 723 that bends the trajectory of the primary beam and travels the secondary beam straight is used. However, the invention is not limited thereto, and the trajectory of the secondary beam travels straight. An inspection apparatus using a Wien filter that bends the wire may be used. In this embodiment, the rectangular beam is formed from the rectangular cathode and the quadrupole lens. However, the present invention is not limited to this. For example, a rectangular beam or an elliptical beam may be created from the circular beam, or the circular beam may be passed through the slit. The rectangular beam may be taken out.
Between the electrode objective lens 724 and the wafer W, an electrode 725 having a shape that is substantially axially symmetric with respect to the irradiation optical axis of the electron beam is disposed. An example of the shape of the electrode 725 is shown in FIGS.

  12 and 13 are perspective views of the electrode 725. FIG. 12 is a perspective view showing a case where the electrode 725 has an axially symmetric cylindrical shape. FIG. 13 shows an electrode 725 that has an axially symmetric disk shape. It is a perspective view which shows a case.

  In the present embodiment, the electrode 725 is described as a cylindrical shape as shown in FIG. 12, but may be a disk shape as shown in FIG. 13 as long as it is substantially axially symmetric with respect to the irradiation optical axis of the electron beam. .

  Further, in order to generate an electric field for preventing discharge between the objective lens 724 and the wafer W, the electrode 725 is applied with a voltage applied to the wafer W (in this embodiment, since it is grounded, the potential is 0 V). A low predetermined voltage (negative potential) is applied by the power source 726. The potential distribution between the wafer W and the objective lens 724 at this time will be described with reference to FIG.

  FIG. 14 is a graph showing a voltage distribution between the wafer W and the objective lens 724.

  In FIG. 14, the voltage distribution from the wafer W to the position of the objective lens 724 is shown with the position on the irradiation optical axis of the electron beam as the horizontal axis.

In the conventional electron beam apparatus without the electrode 725, the voltage distribution from the objective lens 724 to the wafer W changes gently up to the grounded wafer W with the voltage applied to the objective lens 724 as the maximum value. . (Thin line in Fig. 14)
On the other hand, in the electron beam apparatus of this embodiment, an electrode 725 is disposed between the objective lens 724 and the wafer W, and the electrode 725 has a predetermined voltage (negative potential) lower than the voltage applied to the wafer W. Is applied by the power source 726, the electric field of the wafer W is weakened. (Bold line in FIG. 14)
Therefore, in the electron beam apparatus of the present embodiment, the electric field is not concentrated near the via b in the wafer W, and a high electric field does not occur. Even if the via b is irradiated with an electron beam and secondary electrons are emitted, the emitted secondary electrons are not accelerated to the extent that the residual gas is ionized. Discharge can be prevented.

  Further, since discharge between the objective lens 724 and the via b can be prevented, the pattern of the wafer W and the like are not damaged by discharge.

  In the above-described embodiment, discharge between the objective lens 724 and the wafer W having the via b can be prevented. However, since a negative potential is applied to the electrode 725, depending on the magnitude of the negative potential, the detector In some cases, the secondary electron detection sensitivity due to 761 may decrease. Therefore, when the detection sensitivity is lowered, as described above, a series of operations of irradiating an electron beam and detecting secondary electrons are performed a plurality of times, and the obtained detection results are cumulatively added, averaged, etc. To obtain a predetermined detection sensitivity (signal S / N ratio).

In this embodiment, as an example, the detection sensitivity is described as a signal-to-noise ratio (S / N ratio).

  Here, the secondary electron detection operation will be described with reference to FIG.

  FIG. 15 is a flowchart showing the secondary electron detection operation of the electron beam apparatus.

First, secondary electrons from the sample to be inspected are detected by the detector 761 (step 1). Next, it is determined whether the signal-to-noise ratio (S / N ratio) is equal to or greater than a predetermined value (step 2). In step 2, if the signal-to-noise ratio is equal to or greater than the predetermined value, the detection of secondary electrons by the detector 761 is sufficient, and the secondary electron detection operation is completed.

On the other hand, if the signal-to-noise ratio is less than the predetermined value in step 2, a series of operations of irradiating an electron beam and detecting secondary electrons is performed 4N times, and an averaging process is performed (step 3). Here, since the initial value of N is set to “1”, the detection operation of secondary electrons is performed four times in step 3 for the first time.

Next, “1” is added to N and counted up (step 4).
Then, it is determined again whether the signal-to-noise ratio is equal to or greater than a predetermined value. Here, if the signal-to-noise ratio is less than the predetermined value, the process proceeds to step 3 again, and this time the secondary electron detection operation is performed eight times. Then, N is counted up, and steps 2 to 4 are repeated until the signal-to-noise ratio becomes a predetermined value or more.

  In this embodiment, the prevention of discharge of the wafer W having the via b by applying a predetermined voltage (negative potential) lower than the voltage applied to the wafer W to the electrode 725 has been described. Detection efficiency may decrease.

  Therefore, when the sample to be inspected is a type of sample to be inspected such as a wafer having no via, such as a wafer with no via, so that the detection efficiency of secondary electrons in the detector 761 is increased. The voltage applied to the electrode 725 can be controlled.

  Specifically, even when the sample to be tested is grounded, the voltage applied to the electrode 725 is set to a predetermined voltage higher than the voltage applied to the sample to be tested, for example, + 10V. At this time, the distance between the electrode 725 and the sample to be inspected is set such that no discharge occurs between the electrode 725 and the sample to be inspected.

  In this case, secondary electrons generated by irradiating the specimen to be inspected with an electron beam are accelerated to the electron beam source 721 side by an electric field generated by a voltage applied to the electrode 725. Then, the electric field generated by the voltage applied to the objective lens 724 is further accelerated to the electron beam source 721 side and is subjected to a convergence action, so that many secondary electrons enter the detector 761 and increase the detection efficiency. be able to.

  Furthermore, since the electrode 725 is axially symmetric, it also has a lens function for converging the electron beam applied to the sample to be inspected. Therefore, the primary electron beam can be narrowed more narrowly by the voltage applied to the electrode 725. In addition, since the primary electron beam can be narrowed down by the electrode 725, a lower aberration objective lens system can be configured by combining with the objective lens 724. The electrode 725 may be substantially axially symmetric to such an extent that such a lens action is possible.

  According to the electron beam apparatus of the above embodiment, the shape is substantially axisymmetric with respect to the electron beam irradiation axis between the sample to be inspected and the objective lens, and the electron beam irradiation surface of the sample to be inspected is Since the electrode for controlling the electric field strength is provided, the electric field between the sample to be inspected and the objective lens can be controlled.

In addition, an electrode is provided between the sample to be inspected and the objective lens, the electrode being substantially axially symmetric with respect to the electron beam irradiation axis and weakening the electric field intensity on the electron beam irradiation surface of the sample to be inspected. Therefore, the discharge between the sample to be inspected and the objective lens can be eliminated.

Further, since the voltage applied to the objective lens is not changed or the like is not changed, secondary electrons can be passed through the objective lens efficiently, so that detection efficiency can be improved and a signal with a good S / N ratio can be obtained. it can.

Moreover, the voltage for weakening the electric field strength on the electron beam irradiation surface of the sample to be inspected can be controlled depending on the type of the sample to be inspected.

For example, when the specimen to be inspected is a kind of specimen to be inspected that is easily discharged between the objective lens, the voltage of the electrode is changed to further weaken the electric field intensity on the electron beam irradiation surface of the specimen to be inspected. Thus, discharge can be prevented.

Also, depending on the presence or absence of vias in the semiconductor wafer, the voltage applied to the electrodes is changed.
That is, the voltage for weakening the electric field intensity on the electron beam irradiation surface of the semiconductor wafer can be changed.

For example, when the sample to be inspected is a type of sample to be inspected that is easily discharged between the objective lens, the electric field intensity at the electron beam irradiation surface of the sample to be inspected is made weaker by changing the electric field by the electrode. Thus, it is possible to prevent discharge particularly in the via and the periphery of the via.

In addition, since discharge between the via and the objective lens can be prevented, the pattern of the semiconductor wafer or the like is not damaged by discharge.

In addition, since the potential applied to the electrode is lower than the charge applied to the sample to be inspected, the electric field intensity at the electron beam irradiation surface of the sample to be inspected can be weakened, and discharge to the sample to be inspected can be prevented.

Further, since the potential applied to the electrode is set to a negative potential and the sample to be inspected is grounded, the electric field intensity on the electron beam irradiation surface of the sample to be inspected can be weakened and discharge to the sample to be inspected can be prevented.

FIG. 16 shows an EXB separator according to an embodiment of the present invention. FIG. 16 is a cross-sectional view taken along a plane perpendicular to the optical axis. Four pairs of electrodes 701 and 708, 702 and 707, 703 and 706, and 704 and 705 for generating an electric field are formed of nonmagnetic conductors and are substantially cylindrical in shape, and are formed of an insulating material. It is fixed to the inner surface of the support cylinder 713 with a screw (not shown) or the like. The axis of the electrode supporting cylinder 713 and the axis of the cylinder formed by the electrode are aligned with the optical axis 716. A groove 714 parallel to the optical axis 716 is provided on the inner surface of the electrode support cylinder 713 between the electrodes 701, 702, 703, 704, 705, 706, 707 and 708. And the area | region of the inner surface is coated with the conductor 715, and is set to earth potential.

  When an electric field is generated, a voltage proportional to “cos θ1” is applied to the electrodes 702 and 703, “−cos θ1” is applied to the electrodes 706 and 707, “cos θ2” is applied to the electrodes 701 and 704, and “−cos θ2” is applied to the electrodes 705 and 708. Thus, a substantially uniform parallel electric field is obtained in a region of about 60% of the inner diameter of the electrode. FIG. 17 shows the simulation result of the electric field distribution. In this example, four pairs of electrodes are used, but even with three pairs, a uniform parallel electric field can be obtained in a region of about 40% of the inner diameter.

  The magnetic field is generated by arranging two rectangular platinum alloy permanent magnets 709 and 710 in parallel outside the electrode supporting cylinder 713. Protrusions 712 made of a magnetic material are provided around the surfaces of the permanent magnets 709 and 710 on the optical axis 716 side. The projection 712 compensates for the magnetic field lines on the optical axis 716 side being distorted outwardly. Its size and shape can be determined by simulation analysis.

  The outside of the permanent magnets 709 and 710 is a magnetic material made of a ferromagnetic material so that the passage on the side opposite to the optical axis 716 of the magnetic field lines by the permanent magnets 709 and 710 is a cylinder coaxial with the electrode supporting cylinder 713. A circuit 711 is provided.

  The E × B separator as shown in FIG. 16 can be applied not only to the mapping projection type electron beam inspection apparatus as shown in FIG. 8 but also to the scanning type electron beam inspection apparatus.

As is clear from the above description, according to the present embodiment, a region where both the electric field and the magnetic field are uniform around the optical axis can be made large, and even if the irradiation range of the primary electron beam is expanded,
The aberration of the image passing through the E × B separator can be set to a value with no problem.

In addition, since the protrusion is provided in the periphery of the magnetic pole that forms the magnetic field and this magnetic pole is provided outside the electric field generating electrode, a uniform magnetic field can be generated and the electric field distortion due to the magnetic pole can be reduced. Further, since the magnetic field is generated using the permanent magnet, the entire E × B separator can be stored in a vacuum. Furthermore, the entire E × B separator can be miniaturized by forming the electric field generating electrode and the magnetic path forming magnetic circuit into a coaxial cylindrical shape with the optical axis as the central axis.

As shown in FIG. 1, the precharge unit 81 is disposed adjacent to the lens barrel 71 of the electron optical device 70 in the working chamber 31. Since this inspection device is a device that inspects the device pattern formed on the wafer surface by irradiating an electron beam to the substrate to be inspected, that is, the wafer, information such as secondary electrons generated by the irradiation of the electron beam Is the wafer surface information, but the wafer surface may be charged (charged up) depending on conditions such as the wafer material and the energy of irradiated electrons. Further, there may be places where the wafer surface is strongly charged and weakly charged. If the charge amount on the wafer surface is uneven, the secondary electron information is also uneven, and accurate information cannot be obtained. Therefore, in the present embodiment, a precharge unit 81 having a charged particle irradiation unit 811 is provided to prevent this unevenness. Before irradiating inspection electrons to a predetermined portion of the wafer to be inspected, charged particles are irradiated from the charged particle irradiation unit 811 of the precharge unit in order to eliminate uneven charging, thereby eliminating uneven charging. This charge-up of the wafer surface is detected in advance by forming an image of the wafer surface that is symmetrical to the detection, and evaluating the image, and the precharge unit 81 is operated based on the detection.

  In this precharge unit, the primary electron beam may be blurred and irradiated.

    FIG. 18 shows a main part of an embodiment of the precharge unit according to the present invention.

    The charged particles 818 are irradiated from the charged particle irradiation source 819 to the sample substrate W by being accelerated at a voltage set by the bias power source 820. A region to be inspected 815 indicates a location where pre-processed charged particle irradiation has already been performed together with a region 816, and a region 817 indicates a location where charged particle irradiation is being performed. In this figure, the sample substrate W is scanned in the direction of the arrow in the figure. However, when reciprocal scanning is performed, as shown by the dotted line in the figure, another charged particle beam source 819 is placed on the opposite side of the primary electron beam source. The charged particle beam sources 819 and 819 may be turned on and off alternately in synchronization with the scanning direction of the sample substrate W. In this case, if the energy of the charged particles is too high, the secondary electron yield from the insulating part of the sample substrate W will exceed 1, the surface will be positively charged, and even if the secondary electrons are generated below this, the phenomenon will occur. Since it becomes complicated and the irradiation effect decreases, it is effective to set the landing voltage to 100 eV or less (ideally 0 eV or more and 30 eV or less) at which the generation of secondary electrons is drastically reduced.

FIG. 19 shows a second embodiment of the precharge unit according to the present invention. This figure shows an irradiation source of a type that irradiates an electron beam 825 as a charged particle beam. The irradiation source includes a heat filament 821, an extraction electrode 824, a shield case 826, a filament power source 827, and an electron extraction power source 823. The lead electrode 824 has a thickness of 0.1 mm, a slit having a width of 0.2 mm and a length of 1.0 mm, and the positional relationship with the filament 821 having a diameter of 0.1 mm is in the form of a three-electrode electron gun. Yes. The shield case 826 is provided with a slit having a width of 1 mm and a length of 2 mm. The shield case 826 has a distance of 1 mm from the lead electrode 824 and is assembled so that the slit centers coincide with each other. The filament is made of tungsten (W), and a current of 2 A is passed, and an electron current of several μA is obtained at an extraction voltage of 20 V and a bias voltage of −30 V.

The example shown here is one example. For example, the filament material can be refractory metal such as Ta, Ir, Re, Triacoat W, oxide cathode, etc., depending on the material, wire diameter, and length. Needless to say, the filament current changes. Other types of electron guns can be used as long as the electron beam irradiation region, electron current, and energy can be set to appropriate values.

    FIG. 20 shows a third embodiment. An irradiation source of a type that irradiates ions 829 as the charged particle beam is shown. This irradiation source is composed of a filament 821, a filament power source 822, a discharge power source 827, and an anode shield case 826. The anode 828 and the shield case 826 have slits of the same size of 1 mm × 2 mm, and are spaced at intervals of 1 mm. It is assembled so that the centers of both slits coincide. About 1 Pa of Ar gas 830 is introduced into the shield case 826 through the pipe 831, and the arc discharge type using the hot filament 821 is operated. The bias voltage is set to a positive value.

    FIG. 21 shows the case of the plasma irradiation method according to the fourth embodiment. The structure is the same as in FIG. Similarly to the above, the arc discharge type is operated by the hot filament 821, but when the bias potential is set to 0 V, the replasma 832 oozes out from the slit due to the gas pressure and is irradiated to the sample substrate. In the case of plasma irradiation, both the positive and negative surface potentials of the sample substrate surface can be brought close to 0 because of the group of particles having both positive and negative charges as compared with other methods.

    The charged particle irradiation unit 819 arranged close to the sample substrate W has the structure shown in FIGS. 18 to 21, and the difference in the surface structure of the oxide film or nitride film of the sample substrate W or after each different process. Each of the sample substrates is irradiated with charged particles 818 under appropriate conditions. After the sample substrate is irradiated with the optimum irradiation conditions, that is, the potential of the surface of the sample substrate W is measured. Is smoothed or saturated with charged particles, and then an image is formed by electron beams 711 and 712 to detect defects.

    As described above, in this embodiment, the measurement image distortion due to charging does not occur or is small even if it occurs by the process immediately before the measurement by charged particle irradiation, so that the defect can be measured correctly.

In addition, since the stage can be scanned by passing a large amount of current that has been problematic in the past, a large amount of secondary electrons can be detected, a detection signal with a good S / N ratio can be obtained, and the reliability of defect detection Will improve.
Further, since the S / N ratio is large, good image data can be produced even if the stage is scanned earlier, and the inspection throughput can be increased.

    FIG. 22 schematically shows an imaging apparatus including a precharge unit according to the present embodiment. The imaging apparatus includes a primary optical system 72, a secondary optical system 74, a detection system 76, and charge control means 840 that equalizes or reduces the charge charged on the object. The primary optical system 72 is an optical system that irradiates the surface of an inspection target (hereinafter referred to as an object) W with an electron beam, and an electron gun 721 that emits an electron beam and a static electron beam 711 that is deflected from the electron gun 721. An electro lens 722, a Wien filter or E × B polarizer 723 that deflects the primary electron beam so that its optical axis is perpendicular to the surface of the object, and an electrostatic lens 724 that deflects the electron beam. As shown in FIG. 22, the electron gun 721 is placed at the top, and the optical axis of the primary electron beam 711 emitted from the electron gun is inclined with respect to a line perpendicular to the surface (sample surface) of the object W. Are arranged. The E × B deflector 723 includes an electrode 723-1 and a magnet 723-2.

  The secondary optical system 74 includes an electrostatic lens 741 disposed above the E × B type deflector 723 of the primary optical system. The detection system 76 includes a scintillator and microchannel plate (MCP) combination 751 that converts secondary electrons 712 into an optical signal, a CCD 762 that converts an optical signal into an electrical signal, and an image processing device 763. Since the structure and function of each component of the primary optical system 72, the secondary optical system 74, and the detection system 76 are the same as those of the conventional one, detailed description thereof will be omitted.

  In this embodiment, the charge control means 840 for equalizing or reducing the charge charged on the target is applied to the target W between the target W and the electrostatic deflection lens 724 of the primary optical system 72 closest to the target W. An electrode 841 disposed close to the electrode 841, a changeover switch 842 electrically connected to the electrode 841, a voltage generator 844 electrically connected to one terminal 843 of the changeover switch 842, and a changeover switch 842 And a charge detector 846 electrically connected to the other terminal 845. The charge detector 846 has a high impedance. The charge reducing means 840 further includes a grid 847 disposed between the electron gun 721 of the primary optical system 72 and the electrostatic lens 722, and a voltage generator 848 electrically connected to the grid 847. Yes. The timing generator 849 instructs the operation timing to the CCD 762 and the image processing device 763 of the detection system 76, the changeover switch 842 of the charge reducing means 840, the voltage generator 844, and the charge detectors 846 and 848.

  Next, the operation of the electron beam apparatus having the above configuration will be described.

  The primary electron beam 711 emitted from the electron gun 721 reaches the E × B polarizer 723 via the electrostatic lens 722 of the primary optical system 72, and is perpendicular to the surface of the target W by the E × B polarizer 723. Then, the surface (object surface) WF of the object W is irradiated via the electrostatic polarizer 724. Secondary electrons 712 are emitted from the surface WF of the target W according to the properties of the target. The secondary electrons 712 are sent to the combination 751 of the scintillator and MCP of the detection system 76 via the electrostatic lens 741 of the secondary optical system 74, converted into light by the scintillator, and the light is photoelectrically converted by the CCD 762. The image processing device 763 forms a two-dimensional image (having gradation) by the converted electric signal. As in a normal inspection apparatus of this type, the primary electron beam applied to the object is scanned by a known deflection means (not shown) by the primary electron beam, or a table T that supports the object. Is moved in the two-dimensional directions of X and Y, or a combination thereof, and the entire necessary portion on the target surface WF is irradiated to collect data on the target surface.

  Charges are generated near the surface of the target W by the primary electron beam 711 irradiated to the target W, and are positively charged. As a result, the orbits of secondary electrons 712 generated from the surface WF of the target W change according to the state of charge due to the Coulomb force with the charge. As a result, distortion occurs in the image formed in the image processing device 763. Since the charging of the target surface WF varies depending on the properties of the target W, when a wafer is used as the target, even the same wafer is not necessarily the same, and also varies with time. Therefore, there is a possibility that erroneous detection occurs when two patterns on the wafer are compared.

  Therefore, in this embodiment according to the present invention, the CCD 762 of the detection system 76 is arranged in the vicinity of the target W by the charge detector 846 having a high impedance by using the idle time after the image is captured for one scan. The charge amount of the electrode 841 is measured. A voltage for irradiating electrons corresponding to the measured charge amount is generated by the voltage generator 844. After the measurement, the changeover switch 842 is operated to connect the electrode 841 to the voltage generator 844, and the voltage generated by the voltage generator. Is applied to the electrode 841 to cancel charged electrification. As a result, the image formed on the image processing device 763 is prevented from being distorted. Specifically, when a normal voltage is applied to the electrode 841, the focused electron beam is irradiated to the target W. However, if another voltage is applied to the electrode 841, the focusing condition is greatly shifted, and charging is expected. By irradiating a wide area with a small current density and neutralizing the positive charge of a positively charged target, the voltage of a wide area where charging is expected can be made uniform to a specific positive (negative) voltage, By making it uniform and reduced, lower positive (negative) voltage (including zero volts) can be achieved. The canceling operation as described above is performed for each scan.

  The Wehnelt electrode, that is, the grid 847 has a function of stopping the electron beam irradiated from the electron gun 721 during the idle time and stably performing the charge amount measurement and the charge canceling operation. The timing of the above operation is instructed by the timing generator 849 and is, for example, the timing shown in the timing chart of FIG. When a wafer is used as a target, the amount of charge varies depending on the position of the wafer. Therefore, a plurality of sets of electrodes 841, changeover switches 842, voltage generators 844, and charge detectors 846 are provided in the CCD scanning direction to subdivide and more accurately. It is also possible to perform high control.

According to the present embodiment, the following effects can be obtained.
(A) Image distortion caused by charging can be reduced regardless of the properties of the inspection object.
(B) Since the charging is made uniform and offset using the idle time of the conventional measurement timing, the throughput is not affected at all.
(C) Since real-time processing is possible, post-processing time and memory are not required.
(D) High-speed and high-accuracy image observation and defect detection are possible.
FIG. 24 shows a schematic configuration of a defect inspection apparatus including a precharge unit according to another embodiment of the present invention. This defect inspection apparatus includes an electron gun 721 that emits a primary electron beam, an electrostatic lens 722 that deflects and molds the emitted primary electron beam, a sample chamber 32 that can be evacuated to vacuum by a pump (not shown), and is disposed in the sample chamber. The stage 50 is movable in a horizontal plane with a sample such as the semiconductor wafer W placed thereon, and the secondary electron beam and / or the reflected electron beam emitted from the wafer W by the irradiation of the primary electron beam are applied at a predetermined magnification. An electrostatic lens 741 of a projection system for mapping and projecting, a detector 770 for detecting the focused image as a secondary electron image of the wafer, and controlling the entire apparatus and being detected by the detector 770 The control unit 1016 is configured to execute processing for detecting a defect of the wafer W based on the secondary electron image. The secondary electron image includes contributions from not only secondary electrons but also reflected electrons. Here, the secondary electron image is referred to as a secondary electron image.

In the sample chamber 32, a UV lamp 1111 that emits light in a wavelength region including ultraviolet light is installed above the wafer W. The glass surface of the UV lamp 1111 is coated with a photoelectron emitting material 1110 that emits photoelectrons e ⁻ caused by the photoelectric effect by light emitted from the UV lamp 1111. The UV lamp 1111 can be selected from any light source that emits light in a wavelength region having a capability of emitting photoelectrons from the photoelectron emitting material 1110. In general, it is advantageous in terms of cost to use a low-pressure mercury lamp that emits ultraviolet light of 254 nm. The photoelectron emitting material 1110 can be selected from any metal as long as it has the ability to emit photoelectrons. For example, Au is preferable.

  The photoelectrons described above have lower energy than the primary electron beam. Here, low energy means an order of several eV to several tens eV, preferably 0 to 10 eV. The present invention can use any means for generating such low energy electrons. For example, it can also be achieved by providing a low energy electron gun (not shown) instead of the UV lamp 1111.

  Furthermore, the defect inspection apparatus of this embodiment includes a power source 1113. The negative electrode of the power source 1113 is connected to the photoelectron emitting material 1110, and the positive electrode thereof is connected to the stage 50. Accordingly, the photoelectron emitting material 1110 is in a state where a negative voltage is applied to the voltage of the stage 50, that is, the wafer W.

  The detector 770 can have any configuration as long as the secondary electron image formed by the electrostatic lens 741 can be converted into a post-processable signal. For example, as shown in detail in FIG. 46, the detector 770 includes a multi-channel plate 771, a fluorescent screen 772, a relay optical system 773, and an image sensor 774 made up of a number of CCD elements. be able to. The multi-channel plate 771 has a large number of channels in the plate, and generates a larger number of electrons while the secondary electrons imaged by the electrostatic lens 741 pass through the channel. That is, secondary electrons are amplified. The fluorescent screen 772 converts the secondary electrons into light by emitting fluorescence with the amplified secondary electrons. The relay lens 773 guides this fluorescence to the CCD image sensor 774. The CCD image sensor 774 converts the intensity distribution of the secondary electrons on the surface of the wafer W into an electric signal for each element, that is, digital image data, and outputs it to the control unit 1016. To do.

  As illustrated in FIG. 24, the control unit 1016 can be configured by a general-purpose personal computer or the like. This computer includes a control unit main body 1014 that executes various controls and arithmetic processes according to a predetermined program, a CRT 1015 that displays the processing results of the main body 1014, an input unit 1018 such as a keyboard and a mouse for an operator to input commands, Of course, the control unit 1016 may be configured by hardware dedicated to the defect inspection apparatus, a workstation, or the like.

  The control unit body 1014 includes various control boards such as a CPU, RAM, ROM, hard disk, and video board (not shown). On a memory such as a RAM or a hard disk, a secondary electron image storage area 8 for storing an electrical signal received from the detector 770, that is, digital image data of a secondary electron image of the wafer W is allocated. In addition to a control program for controlling the entire defect inspection apparatus, secondary electron image data is read from the storage area 1008 on the hard disk, and defects on the wafer W are automatically detected according to a predetermined algorithm based on the image data. A defect detection program 1009 is stored. For example, the defect detection program 1009 has a function of comparing the inspection location of the wafer W with another inspection location, and displaying a warning pattern as a defect for a pattern that is different from the pattern at most other locations. Further, a secondary electron image 1017 may be displayed on the display unit of the CRT 1015, and the defect of the wafer W may be detected by visual observation by the operator.

  Next, the operation of the electron beam apparatus according to the embodiment in FIG. 24 will be described using the flowchart in FIG. 27 as an example.

First, the wafer W to be inspected is set on the stage 50 (step 1200). This may be a form in which a large number of wafers W stored in a loader (not shown) are automatically set on the stage 50 one by one. Next, a primary electron beam is emitted from the electron gun 721, and irradiated to a predetermined inspection region on the set wafer W surface through the electrostatic lens 722 (step 1202). Secondary electrons and / or reflected electrons (hereinafter referred to as “secondary electrons”) are emitted from the wafer W irradiated with the primary electron beam, and as a result, the wafer W is charged up to a positive potential. Next, the generated secondary electron beam is imaged on the detector 770 at a predetermined magnification by the electrostatic lens 741 of the magnifying projection system (step 1204). At this time, the UV lamp 1111 is caused to emit light while a negative voltage is applied to the photoelectron emitting material 1110 from the stage 50 (step 1206). As a result, ultraviolet light having a frequency ν emitted from the UV lamp 1111 emits photoelectrons from the photoelectron emitting material 1110 by the energy quantum hν (h is Planck's constant). These photoelectrons e ⁻ are irradiated from the negatively charged photoelectron emitting material 1110 toward the positively charged wafer W to electrically neutralize the wafer W. Thus, the secondary electron beam is imaged on the detector 770 without being substantially affected by the positive potential of the wafer W.

  The detector 770 detects the secondary electron beam image with reduced image disturbance emitted from the wafer W thus electrically neutralized, and converts it into digital image data (step 1208). Next, the control unit 1016 executes a defect detection process for the wafer W based on the detected image data in accordance with the defect detection program 1009 (step 1210). In this defect detection process, in the case of a wafer having a large number of the same dies, the control unit 1016 extracts a defect portion by comparing the detected images of the detected dies as described above. A defective secondary portion may be automatically detected by comparing and comparing a reference secondary electron beam image of a wafer that has been stored in advance in a memory and has no defects and an actually detected secondary electron beam image. At this time, the detected image may be displayed on the CRT 1015 and a portion determined to be a defective portion may be displayed as a mark, whereby the operator finally confirms and evaluates whether or not the wafer W actually has a defect. can do. A specific example of this defect detection method will be described later.

  As a result of the defect detection process in step 1210, when it is determined that the wafer W has a defect (step 1212 affirmative determination), the operator is warned of the presence of the defect (step 1218). As a warning method, for example, a message notifying the presence of a defect may be displayed on the display unit of the CRT 1015, or at the same time, an enlarged image 1017 of a pattern having a defect may be displayed. Such a defective wafer may be immediately taken out from the sample chamber 32 and stored in a storage place different from the wafer having no defect (step 1219).

  As a result of the defect detection process in step 1210, if it is determined that the wafer W has no defect (No in step 1212), whether or not there is still an area to be inspected for the wafer W currently being inspected. A determination is made (step 1214). When the region to be inspected remains (Yes in Step 1214), the stage 50 is driven, and the wafer W is moved so that the other region to be inspected now falls within the irradiation region of the primary electron beam (Step 1216). . Thereafter, the process returns to step 1202 and the same processing is repeated for the other inspection regions.

  If the area to be inspected does not remain (No at step 1214), or after the defective wafer extraction step (step 1219), whether or not the wafer W currently being inspected is the final wafer, That is, it is determined whether an uninspected wafer remains in a loader (not shown) (step 1220). If it is not the final wafer (No at Step 1220), the inspected wafer is stored in a predetermined storage location, and a new uninspected wafer is set on the stage 50 instead (Step 1222). Thereafter, the process returns to step 1202 and the same processing is repeated for the wafer. If it is the final wafer (Yes at step 1220), the inspected wafer is stored in a predetermined storage location, and the entire process is completed.

  UV photoelectron irradiation (step 1206) is performed at an arbitrary timing and within an arbitrary period as long as positive charge-up of the wafer W is avoided and secondary electron image detection (step 1206) can be performed in a state in which image disturbance is reduced. be able to. While the processing of FIG. 27 is continued, the UV lamp 1111 may be constantly turned on, but the light emission and extinction may be repeated by setting a period for each wafer. In the latter case, the timing of light emission is started before the execution of secondary electron beam imaging (step 1204) and before the execution of primary electron beam irradiation (step 1202) in addition to the timing shown in FIG. Also good. Although UV photoelectron irradiation is preferably continued at least during the secondary electron detection period, UV photoelectron irradiation can be performed if the wafer is sufficiently neutralized before or during detection of the secondary electron image. May be stopped.

  Specific examples of the defect detection method in step 1210 are shown in FIGS. First, FIG. 28A shows an image 1231 of the die detected first and an image 1232 of the other die detected second. If the image of another die detected third is determined to be the same as or similar to the first image 1231, it is determined that the portion 1233 of the second die image 1232 has a defect, and the defective portion is detected. it can.

  FIG. 28B shows an example of measuring the line width of the pattern formed on the wafer. When the actual pattern 1234 on the wafer is scanned in the direction of 1235, the actual secondary electron intensity signal is 1236, and this signal continuously exceeds the threshold level 1237 determined by calibration. Can be measured as the line width of the pattern 1234. When the measured line width is not within the predetermined range, it can be determined that the pattern has a defect.

  FIG. 28C shows an example in which the potential contrast of the pattern formed on the wafer is measured. In the configuration shown in FIG. 24, an axially symmetric electrode 1239 is provided above the wafer W, and, for example, a potential of −10 V is applied to the wafer potential of 0 V. At this time, the −2 V equipotential surface has a shape indicated by 1240. Here, it is assumed that the patterns 1241 and 1242 formed on the wafer have potentials of −4 V and 0 V, respectively. In this case, the secondary electrons emitted from the pattern 1241 have an upward velocity corresponding to kinetic energy of 2 eV at the −2 V equipotential surface 1240, so that the electrode crosses the potential barrier 1240 and appears as shown by the orbit 1243. Escape from 1239 and detected by detector 770. On the other hand, the secondary electrons emitted from the pattern 1242 are not detected because they cannot cross the −2V potential barrier and are driven back to the wafer surface as indicated by the trajectory 1244. Therefore, the detection image of the pattern 1241 is bright and the detection image of the pattern 1242 is dark. Thus, a potential contrast is obtained. If the brightness and potential of the detected image are calibrated in advance, the pattern potential can be measured from the detected image. The defect portion of the pattern can be evaluated from this potential distribution.

  FIG. 25 shows a schematic configuration of a defect inspection apparatus provided with a precharge unit according to another embodiment of the present invention. Note that the same components as those in the embodiment of FIG. 24 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, as shown in FIG. 25, the glass surface of the UV lamp 1111 is not coated with a photoelectron emitting material. Instead, the photoelectron emission plate 1110b is disposed above the wafer W in the sample chamber 322, and the UV lamp 1111 is disposed at a position where the emitted ultraviolet light is irradiated onto the photoelectron emission plate 1110b. The negative electrode of the power source 13 is connected to the photoelectron emission plate 1110b, and the positive electrode of the power source is connected to the stage 50. The photoelectron emission plate 1110b may be made of a metal such as Au, or may be made as a plate coated with such a metal.

  The operation of the embodiment of FIG. 25 is the same as that of the embodiment of FIG. In the embodiment of FIG. 25 as well, since the photoelectrons can be irradiated onto the surface of the wafer W in a timely manner, the same effects as those of the embodiment of FIG.

  FIG. 26 shows a schematic configuration of a defect inspection apparatus including a precharge unit according to still another embodiment of the present invention. Components similar to those in the embodiment of FIGS. 24 and 25 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the embodiment shown in FIG. 26, as shown in FIG. 26, a transparent window member 1112 is provided on the side wall of the sample chamber 32, and ultraviolet rays emitted from the UV lamp 1111 pass through the window member 1112 in the sample chamber 32. A UV lamp 1111 is disposed outside the sample chamber 32 so as to irradiate the photoelectron emission plate 1110 b disposed above the sample chamber 32. In the embodiment of FIG. 26, since the UV lamp 1111 is disposed outside the sample chamber 32 that is in a vacuum, it is not necessary to consider the vacuum resistance performance of the UV lamp 1111, compared with the embodiment of FIGS. 24 and 25. Options for the UV lamp 1111 can be expanded.

  Other operations of the embodiment of FIG. 26 are the same as those of the embodiment of FIGS. In the embodiment of FIG. 26 as well, since the photoelectrons can be irradiated onto the surface of the wafer W in a timely manner, the same effects as those of the embodiments of FIGS.

  Although the above is each said embodiment, the defect inspection apparatus provided with the precharge unit by this invention is not limited only to the said example, It can change arbitrarily suitably within the scope of the summary of this invention.

  For example, the semiconductor wafer W is taken as an example of the sample to be inspected, but the sample to be inspected according to the present invention is not limited to this, and any one that can detect a defect with an electron beam can be selected. For example, a mask or the like on which a pattern for exposing a wafer is formed can be an inspection target.

  Further, although the configuration of FIGS. 24 to 26 is shown as the electron beam apparatus for defect inspection, the electron optical system and the like can be arbitrarily and suitably changed. For example, the electron beam irradiation means (721, 722) of the illustrated defect inspection apparatus is a type in which a primary electron beam is incident on the surface of the wafer W obliquely from above, but the primary electrons are below the electrostatic lens 741. A line deflecting unit may be provided so that the primary electron beam is incident on the surface of the wafer W perpendicularly. As such a deflecting means, for example, there is a Wien filter that deflects a primary electron beam by a field E × B in which an electric field and a magnetic field are orthogonal to each other.

  Furthermore, as a means for emitting photoelectrons, it is needless to say that any means other than the combination of the UV lamp 1111 and the photoelectron emission member 1110 or the photoelectron emission plate 1110b shown in FIGS. 24 to 26 can be adopted.

  Further, the flow of the flowchart of FIG. 27 is not limited to this. For example, the sample determined to have a defect in step 1212 is not subjected to defect inspection in other regions, but the processing flow may be changed so as to detect defects covering the entire region. Further, if the irradiation region of the primary electron beam can be enlarged and the entire inspection region of the sample can be covered with one irradiation, Step 1214 and Step 1216 can be omitted.

  Further, in FIG. 27, if it is determined in step 1212 that the wafer has a defect, the operator immediately warns the presence of the defect in step 1218 and performs post-processing (step 1219). Later (after affirmative determination in step 1220), the process flow may be changed to report defect information of a wafer having defects.

  As described in detail above, according to the defect inspection apparatus and the defect inspection method according to the embodiments of FIGS. 24 to 26, electrons having lower energy than the primary electron beam are supplied to the sample. The positive charge-up of the sample surface due to the emission is reduced, and as a result, the image defect of the secondary electron beam accompanying the charge-up can be eliminated, and the defect of the sample can be inspected with higher accuracy. An excellent effect is obtained.

Further, according to the device manufacturing method using the defect inspection apparatus of FIGS. 24 to 26, since the defect inspection of the sample is performed using the defect inspection apparatus as described above, the yield of the product is improved and the defect product is improved. An excellent effect of preventing shipment can be obtained.
In FIG. 29, the potential applying mechanism 83 is based on the fact that the secondary electron information (secondary electron generation rate) emitted from the wafer depends on the potential of the wafer. The generation of secondary electrons is controlled by applying a potential of ± several V to the installation table. In addition, this potential application mechanism also serves to reduce the energy initially possessed by the irradiated electrons so that the irradiated electron energy is about 100 to 500 eV on the wafer.

  As shown in FIG. 29, the potential application mechanism 83 includes a voltage application device 831 that is electrically connected to the mounting surface 541 of the stage apparatus 50, and a charge-up investigation and voltage determination system (hereinafter, investigation and determination system) 832. And. The investigation and determination system 832 includes a monitor 833 electrically connected to the image forming unit 763 of the detection system 76 of the electro-optical device 70, an operator 834 connected to the monitor 833, and a CPU 835 connected to the operator 834. I have. The CPU 835 supplies a signal to the voltage applying device 831.

  The potential application mechanism is designed to search for a potential at which a wafer to be inspected is difficult to be charged and apply the potential.

  As a method for inspecting an electrical defect of an inspection sample, it is also possible to use the fact that the voltage of the part is different when the part that is originally electrically insulated and the part are in an energized state.

First, by applying a charge to the sample in advance, the voltage of the part that is originally electrically insulated and the part that is originally electrically insulated, but the part that is in an energized state for some reason By generating a voltage difference with the voltage and then irradiating the beam of the present invention, data having a voltage difference is acquired, and the acquired data is analyzed to detect that the current state is energized.
Electron Beam Calibration Mechanism In FIG. 30, an electron beam calibration mechanism 85 includes a plurality of Faraday cups for measuring beam currents installed at a plurality of locations on the side of the wafer mounting surface 541 on the rotary table 54. 851 and 852 are provided. The Faraday cup 851 is for a thin beam (about φ2 μm), and the Faraday cup 852 is for a thick beam (about φ30 μm). In the Faraday cup 851 for a thin beam, the beam profile is measured by step-feeding the rotary table 54. The Faraday cup 852 for the thick beam measures the total current amount of the beam. The Faraday cups 851 and 852 are arranged so that the upper surface thereof is at the same level as the upper surface of the wafer W placed on the placement surface 541. In this way, the primary electron beam emitted from the electron gun is constantly monitored. This is because the electron gun cannot always emit a constant electron beam, and the amount of emission changes during use.
Alignment control device The alignment control device 87 is a device for positioning the wafer W with respect to the electro-optical device 70 using the stage device 50, and roughly aligning the wafer by wide-field observation using the optical microscope 871 (electro-optical system) Measurement with a lower magnification than the above), and high magnification adjustment, focus adjustment, inspection area setting, pattern alignment, and the like are controlled using the electron optical system of the electron optical device 70. Inspecting the wafer at a low magnification using the optical system in this way is to perform wafer alignment by observing the wafer pattern in a narrow field of view using an electron beam in order to automatically inspect the wafer pattern. This is because it is necessary to easily detect the alignment mark with an electron beam when performing.

  The optical microscope 871 is provided in the housing (may be provided so as to be movable in the housing), and a light source for operating the optical microscope is also provided in the housing although not shown. An electron optical system that performs high-magnification observation shares the electron optical system (the primary optical system 72 and the secondary optical system 74) of the electron optical device 70. A schematic diagram of the configuration is shown in FIG. In order to observe the observation point on the wafer at a low magnification, the observation point on the wafer is moved into the field of view of the optical microscope by moving the X stage 53 of the stage apparatus 50 in the X direction. The optical microscope 871 visually recognizes the wafer with a wide field of view, and the position to be observed on the wafer is displayed on the monitor 873 via the CCD 872 to roughly determine the observation position. In this case, the magnification of the optical microscope may be changed from a low magnification to a high magnification.

Next, the stage device 50 is moved by a distance corresponding to the distance δx between the optical axis of the electron optical device 70 and the optical axis of the optical microscope 871, and the observation point on the wafer predetermined by the optical microscope is moved to the position of the electron optical device. Move to field of view. In this case, the distance between the axis O ₃ -O _{3 of} the electron optical device and the optical axis O ₄ -O ₄ of the optical microscope 871 (in this embodiment, both are displaced only in the direction along the X axis). (Although it may be displaced in the Y-axis direction and the Y-axis direction.) Δx is known in advance, the observation point can be moved to the visual recognition position by moving the value δx. After the movement of the observation point to the visual recognition position of the electron optical device is completed, the observation point is imaged by SEM at a high magnification by the electron optical system, and the image is stored or displayed on the monitor 765 via the CCD 761.

In this way, after the observation point of the wafer is displayed on the monitor at a high magnification by the electron optical system, the positional deviation electron optical system in the rotation direction of the wafer with respect to the rotation center of the rotary table 54 of the stage apparatus 50 is known. A deviation δθ in the rotation direction of the wafer with respect to the optical axis O ₃ -O ₃ is detected, and a positional deviation in the X axis and Y axis directions of a predetermined pattern relating to the electro-optical device is detected. Then, the wafer alignment is performed by controlling the operation of the stage device 50 based on the detected value and the data on the inspection mark provided on the wafer or the data on the pattern of the wafer obtained separately.
The evacuation system is composed of a vacuum pump, a vacuum valve, a vacuum gauge, a vacuum pipe, and the like, and evacuates the electron optical system, the detector section, the sample chamber, and the load lock chamber according to a predetermined sequence. In each part, the vacuum valve is controlled so as to achieve a required degree of vacuum. The vacuum level is constantly monitored, and when an abnormality occurs, emergency control of the isolation valve, etc. is performed by an interlock function to ensure the vacuum level. As a vacuum pump, a turbo molecular pump for main exhaust,
A roots type dry pump is used for roughing. The pressure of the inspection place (electron beam irradiation part) is 10 ⁻³ to 10 ⁻⁵ Pa, preferably 10 ⁻⁴ to 10 ⁻⁶ Pa, which is one digit lower than that.
The control system control system mainly includes a main controller, a control controller, and a stage controller.

  The main controller is equipped with a man-machine interface, through which operator operations are performed (various instructions / commands, recipe input, inspection start instructions, automatic and manual inspection mode switching, manual inspection mode, etc. Input of all necessary commands at the time). In addition, communication with the host computer in the factory, control of the evacuation system, sample transfer of wafers, alignment control, command transmission to other control controllers and stage controllers, reception of information, etc. are also performed by the main controller. . In addition, acquisition of image signals from an optical microscope, stage vibration correction function that feeds back stage fluctuation signals to the electron optical system to correct image deterioration, and the Z direction of the sample observation position (axial direction of the secondary optical system) It has an automatic focus correction function that detects the displacement, feeds back to the electron optical system, and automatically corrects the focus. Transmission / reception of a feedback signal and the like to the electron optical system and transmission / reception of a signal from the stage are performed via a control controller and a stage controller, respectively.

  The control controller is mainly responsible for control of the electron beam optical system (control of high-precision power sources for electron guns, lenses, aligners, Wien filters, etc.). Specifically, each operation mode, such as ensuring that the irradiation area is always irradiated with a constant electron current even when the magnification changes, and automatically setting the voltage to each lens system and aligner corresponding to each magnification. Control (interlocking control) such as automatic voltage setting for each lens system and aligner corresponding to is performed.

The stage controller mainly controls the movement of the stage to enable precise movement in the X and Y directions in the order of μm (error of about ± 0.5 μm). Further, in this stage, the rotation direction control (θ control) is also performed within an error accuracy of about ± 0.3 seconds.
Electrode cleaning When the electron beam apparatus of the present invention is operated, the target substance is floated and attracted to the high-pressure region by proximity interaction (charging of particles near the surface), so that various types of electron beam formation and deflection are used. Organic materials are deposited on these electrodes. Insulators that gradually accumulate due to surface charging adversely affect the formation and deflection mechanism of the electron beam, so the deposited insulators must be removed periodically. Periodic removal of the insulator is performed by using an electrode in the vicinity of the region where the insulator is deposited, such as hydrogen, oxygen, fluorine, and a compound HF, O ₂ , H ₂ O, C _{MF N,} etc. containing them in a vacuum. By creating plasma and maintaining the plasma potential in the space at a potential (several kV, for example, 20 V to 5 kV) at which sputtering occurs on the electrode surface, only organic substances are removed by oxidation, hydrogenation, and fluorination.

Modification of the stage device Figure 32 shows a variant of a stage device in the sensor according to the present invention.

  A partition plate 914 extending substantially horizontally in the + Y direction and the −Y direction (left-right direction in FIG. 32B) is attached to the upper surface of the Y-direction movable portion 95 of the stage 93. A diaphragm portion 950 having a small conductance is always formed between the two. In addition, a similar partition plate 912 is also formed on the upper surface of the X-direction movable portion 96 so as to project in the ± X direction (left and right direction in FIG. 32 [A]). An aperture 951 is formed. The stage base 97 is fixed on the bottom wall in the housing 98 by a known method.

Therefore, the throttle portions 950 and 951 are always formed regardless of the position of the sample stage 94. Therefore, even if gas is released from the guide surfaces 96a and 97a when the movable portions 95 and 96 are moved, the throttle portion 950 is formed. 951 prevents the movement of the emitted gas, so that the pressure increase in the space 924 near the sample irradiated with the charged beam can be suppressed to a very small level.

A differential evacuation groove as shown in FIG. 56 is formed around the hydrostatic bearing 90 on the side surface and the lower surface of the movable portion 95 of the stage and the lower surface of the movable portion 96, and evacuated by this groove. Therefore, when the throttle portions 950 and 951 are formed, the gas discharged from the guide surface is mainly exhausted by these differential exhaust portions. For this reason, the pressure in the spaces 913 and 915 inside the stage is higher than the pressure in the chamber C. Therefore, not only the spaces 913 and 915 are exhausted by the differential exhaust grooves 917 and 918, but if a place to be evacuated is provided separately, the pressure in the spaces 913 and 915 can be reduced, and the pressure increase in the vicinity of the sample 924 can be reduced. It can be further reduced. For this purpose, vacuum exhaust passages 91-1 and 91-2 are provided. The exhaust passage passes through the stage base 97 and the housing 98 and communicates with the outside of the housing 98. Further, the exhaust passage 91-2 is formed in the X-direction movable portion 96 and opens on the lower surface of the X-direction movable portion 96.

  Further, when the partition plates 912 and 914 are installed, it is necessary to enlarge the chamber so that the chamber C and the partition plate do not interfere with each other. However, this point can be improved by making the partition plate an expandable material or structure. Is possible. In this embodiment, the partition plate is made of rubber or has a bellows shape, and the end in the moving direction is the X-direction movable portion 96 in the case of the partition plate 914, and the inner wall of the housing 98 in the case of the partition plate 912. It is conceivable to adopt a configuration in which each is fixed.

  In FIG. 33, the 2nd modification of a stage apparatus is shown.

In this embodiment, a cylindrical partition 916 is formed around the tip of the lens barrel, that is, around the charged beam irradiation unit 72 so that a constriction is formed between the upper surface of the sample W. In such a configuration, even if gas is released from the XY stage and the pressure in the chamber C rises, the interior 924 of the partition is partitioned by the partition 916 and is exhausted by the vacuum pipe 910. And a pressure difference between the interior 924 of the partition and the pressure rise in the space 924 inside the partition can be kept low. The gap between the partition 916 and the sample surface varies depending on how much pressure is maintained in the chamber C and around the irradiation unit 72, but about several tens μm to several mm is appropriate. The inside of the partition 916 and the vacuum pipe are communicated by a known method.

Further, in the charged beam irradiation apparatus, a high voltage of about several kV may be applied to the sample W, and if a conductive material is placed in the vicinity of the sample, there is a risk of causing discharge. In this case, if the partition 916 is made of an insulating material such as ceramics, no discharge will occur between the sample W and the partition 916.

  Note that the ring member 94-1 disposed around the sample W (wafer) is a plate-like adjustment component fixed to the sample stage 94, and is a case where a charged beam is irradiated to the end of the sample such as a wafer. However, it is set to the same height as the wafer so that a minute gap 952 is formed over the entire periphery of the tip of the partition 916. As a result, no matter where the sample W is irradiated with the charged beam, a constant minute gap 952 is always formed at the tip of the partition 916, and the pressure in the space 924 around the tip of the lens barrel can be kept stable. it can.

  In FIG. 34, another modification is shown.

  A partition 919 incorporating a differential exhaust structure is provided around the charged beam irradiation unit 72 of the lens barrel 71. The partition 919 has a cylindrical shape, and a circumferential groove 920 is formed therein, and an exhaust passage 921 extends upward from the circumferential groove. The exhaust passage is connected to a vacuum pipe 923 via an internal space 922. A minute gap of about several tens of μm to several mm is formed between the lower end of the partition 919 and the upper surface of the sample W.

  In such a configuration, even when the gas is released from the stage as the stage moves and the pressure in the chamber C rises and the gas tries to flow into the tip, that is, the charged beam irradiation unit 72, the partition 919 is separated from the sample W. Since the conductance is very small by narrowing the gap, the inflow of gas is disturbed and the amount of inflow is reduced. Further, since the inflowing gas is exhausted from the circumferential groove 920 to the vacuum pipe 923, almost no gas flows into the space 924 around the charged beam irradiation unit 72, and the pressure of the charged beam irradiation unit 72 is increased to a desired high level. A vacuum can be maintained.

  FIG. 35 shows still another modification.

  A partition 926 is provided around the chamber C and the charged beam irradiation unit 72 to separate the charged beam irradiation unit 72 from the chamber C. The partition 926 is connected to the refrigerator 930 through a support member 929 made of a material having good thermal conductivity such as copper or aluminum, and is cooled to about −100 ° C. to −200 ° C. The member 927 is for inhibiting heat conduction between the cooled partition 926 and the lens barrel, and is made of a material having poor heat conductivity such as ceramics or a resin material. The member 928 is made of a non-insulator such as ceramics and is formed at the lower end of the partition 926 and has a role of preventing the sample W and the partition 926 from discharging.

  With such a configuration, gas molecules that are about to flow into the charged beam irradiation unit from inside the chamber C are blocked by the partition 926, and even if they flow, they are frozen and collected on the surface of the partition 926. The pressure of the charged beam irradiation unit 924 can be kept low.

  As the refrigerator, a refrigerator such as cooling with liquid nitrogen, a He refrigerator, a pulse tube refrigerator or the like can be used.

  In FIG. 36, still another modification is shown.

  Both movable parts of the stage 93 are provided with partition plates 912 and 914 in the same manner as shown in FIG. 32, and even if the sample stage 94 moves to an arbitrary position, the space in the stage is separated by these partitions. 913 and the inside of the chamber C are partitioned through throttles 950 and 951. Further, a partition 916 similar to that shown in FIG. 33 is formed around the charged beam irradiation unit 72, and the space 924 in the chamber C and the charged beam irradiation unit 72 is partitioned through a diaphragm 952. Yes. For this reason, when the stage is moved, even if the gas adsorbed on the stage is released into the space 913 and the pressure in this portion is raised, the pressure rise in the chamber C is kept low, and the pressure rise in the space 924 is kept even lower. It is done. Thereby, the pressure of the charged beam irradiation space 924 can be kept low. Further, by using a partition 919 with a built-in differential exhaust mechanism as shown in the partition 916 or a partition 926 cooled by a refrigerator as shown in FIG. 34, the space 924 can be made stable at a lower pressure. Can be maintained.

According to these embodiments, the following effects can be obtained.
(A) The stage device can exhibit highly accurate positioning performance in a vacuum, and the pressure at the charged beam irradiation position is unlikely to increase. That is, it is possible to perform processing with a charged beam on a sample with high accuracy.
(B) The gas released from the static pressure bearing support can hardly pass through the partition to the charged beam irradiation region side. As a result, the degree of vacuum at the charged beam irradiation position can be further stabilized.
(C) It becomes difficult for the emitted gas to pass to the charged beam irradiation region side, and the degree of vacuum in the charged beam irradiation region is easily kept stable.
(D) The inside of the vacuum chamber is divided into three chambers, a charged beam irradiation chamber, a static pressure bearing chamber, and an intermediate chamber thereof, through a small conductance. Then, the evacuation system is configured so that the pressure in each chamber becomes the charged beam irradiation chamber, the intermediate chamber, and the static pressure bearing chamber in order from the lowest. The pressure fluctuation to the intermediate chamber is further suppressed by the partition, and the pressure fluctuation to the charged beam irradiation chamber is further reduced by the other partition, and it becomes possible to reduce the pressure fluctuation to a level at which there is substantially no problem. .
(E) It becomes possible to suppress the pressure rise when the stage moves.
(F) It is possible to further suppress the pressure increase when the stage moves.
(G) Since it is possible to realize an inspection device with high stage positioning performance and a stable degree of vacuum in the charged beam irradiation area, an inspection device with high inspection performance and no risk of contaminating the sample is provided. can do.
(H) Since an exposure apparatus with high stage positioning performance and a stable vacuum degree in the charged beam irradiation region can be realized, an exposure apparatus with high exposure accuracy and no risk of contaminating the sample is provided. be able to.
(L) A fine semiconductor circuit can be formed by manufacturing a semiconductor with an apparatus having a high stage positioning performance and a stable vacuum degree in the charged beam irradiation region.

    It is obvious that the stage apparatus of FIGS. 32-36 can be applied to the stage 50 of FIG.

  Another embodiment of the XY stage according to the present invention will be described with reference to FIGS. Note that the reference numerals indicating the common members in the conventional example and the embodiment in FIG. 55 are the same. In this specification, “vacuum” is a vacuum called in the technical field, and does not necessarily indicate an absolute vacuum.

  In FIG. 37, another embodiment of the XY stage is shown.

  A distal end portion of a lens barrel 71 that irradiates a charged beam toward a sample, that is, a charged beam irradiation portion 72 is attached to a housing 98 that defines a vacuum chamber C. A sample W placed on a movable table in the X direction (left and right direction in FIG. 37) of the XY stage 93 is arranged immediately below the lens barrel 71. The sample W can be accurately irradiated with a charged beam at an arbitrary position on the sample surface by a highly accurate XY stage 93.

  A pedestal 906 of the XY stage 93 is fixed to the bottom wall of the housing 98, and a Y table 95 moving in the Y direction (direction perpendicular to the paper surface in FIG. 37) is placed on the pedestal 906. On both side surfaces (left and right side surfaces in FIG. 37) of the Y table 95, protrusions projecting into recessed grooves formed on the side facing the Y table of the pair of Y direction guides 907a and 907b mounted on the pedestal 906. Is formed. The concave groove extends in the Y direction over substantially the entire length of the Y direction guide. Static pressure bearings 911a, 909a, 911b, and 909b having a known structure are respectively provided on the upper, lower, and side surfaces of the protrusion protruding into the groove, and high pressure gas is blown through these static pressure bearings. The Y table 95 is supported in a non-contact manner with respect to the Y direction guides 907a and 907b, and can smoothly reciprocate in the Y direction. A linear motor 932 having a known structure is disposed between the pedestal 906 and the Y table 95, and driving in the Y direction is performed by the linear motor. High pressure gas is supplied to the Y table by a flexible pipe 934 for supplying high pressure gas, and high pressure is applied to the static pressure bearings 909a to 911a and 909b to 911b through a gas passage (not shown) formed in the Y table. Gas is supplied. The high-pressure gas supplied to the hydrostatic bearing is jetted into a gap of several microns to several tens of microns formed between the opposing guide surfaces of the Y-direction guide, and the Y table is guided in the X and Z directions with respect to the guide surface. It plays a role of accurately positioning in the direction (vertical direction in FIG. 37).

  An X table 96 is placed on the Y table so as to be movable in the X direction (left and right direction in FIG. 37). On the Y table 95, a pair of X direction guides 908a and 908b (only 908a is shown) having the same structure as the Y direction guides 907a and 907b for the Y table are provided with the X table 96 interposed therebetween. A groove is also formed on the side of the X direction guide facing the X table, and a protrusion projecting into the groove is formed on the side of the X table (side facing the X direction guide). The concave groove extends substantially over the entire length of the X-direction guide. Static pressure bearings (not shown) similar to the static pressure bearings 911a, 909a, 910a, 911b, 909b, 910b are the same on the upper, lower and side surfaces of the X-direction table 96 protruding into the concave groove. It is provided by arrangement. A linear motor 933 having a known structure is disposed between the Y table 95 and the X table 96, and the X table is driven in the X direction by the linear motor. A high pressure gas is supplied to the X table 96 through a flexible pipe 931, and the high pressure gas is supplied to the static pressure bearing. The high pressure gas is ejected from the static pressure bearing to the guide surface of the X direction guide, whereby the X table 96 is supported in a non-contact manner with respect to the Y direction guide with high accuracy. The vacuum chamber C is exhausted by vacuum pipes 919, 920a, and 920b connected to a vacuum pump or the like having a known structure. The inlet side (inside the vacuum chamber) of the pipes 920a and 920b passes through the pedestal 906 and opens on the top surface near the position where the high-pressure gas is discharged from the XY stage 93. The pressure in the vacuum chamber is static pressure. It is prevented as much as possible from rising due to the high-pressure gas ejected from the bearing.

  A differential pumping mechanism 925 is provided around the tip of the lens barrel 71, that is, around the charged beam irradiation unit 72, so that the pressure in the charged beam irradiation space 930 is sufficiently low even if the pressure in the vacuum chamber C is high. is there. That is, the annular member 926 of the differential exhaust mechanism 925 attached around the charged beam irradiation unit 72 has a minute gap (several microns to several hundred microns) 940 between the lower surface (surface on the sample W side) and the sample. As formed, it is positioned with respect to the housing 98, and an annular groove 927 is formed on the lower surface thereof. The annular groove 927 is connected to an unillustrated vacuum pump or the like by an exhaust pipe 928. Therefore, the minute gap 940 is exhausted through the annular groove 927 and the exhaust port 928, and even if gas molecules try to enter the space 930 surrounded by the annular member 926 from the vacuum chamber C, the minute gap 940 is exhausted. Thereby, the pressure in the charged beam irradiation space 930 can be kept low, and the charged beam can be irradiated without any problem.

  The annular groove may have a double structure or a triple structure depending on the pressure in the chamber and the pressure in the charged beam irradiation space 930.

  Generally, dry nitrogen is used as the high-pressure gas supplied to the hydrostatic bearing. However, if possible, it is preferable to use a higher purity inert gas. This is because if impurities such as moisture and oil are contained in the gas, these impurity molecules adhere to the inner surface of the housing and the surface of the stage components that define the vacuum chamber, and the degree of vacuum is deteriorated. This is because the degree of vacuum of the charged beam irradiation space is deteriorated by adhering to the surface.

  In the above description, the sample W is not usually placed directly on the X table, but is provided with functions such as holding the sample in a removable manner and performing a slight position change with respect to the XY stage 93. Although it is placed on the sample table, the presence or absence of the sample table and the structure thereof are not related to the gist of the present embodiment, and are omitted for the sake of simplicity.

  In the charged beam apparatus described above, since the stage mechanism of the static pressure bearing used in the atmosphere can be used almost as it is, the high-precision XY stage equivalent to the high-precision stage for the atmosphere used in the exposure apparatus or the like is almost This can be realized for an XY stage for a charged beam apparatus at the same cost and size.

  The structure and arrangement of the static pressure guide and the actuator (linear motor) described above are merely examples, and any static pressure guide or actuator that can be used in the atmosphere can be applied.

  Next, FIG. 38 shows a numerical example of the size of the annular member 926 of the differential exhaust mechanism and the annular groove formed thereon. In this example, the annular groove has a double structure of 927a and 927b, which are separated in the radial direction.

The flow rate of the high-pressure gas supplied to the static pressure bearing is usually about 20 L / min (atmospheric pressure conversion). Assuming that the vacuum chamber C is evacuated with a dry pump having an evacuation rate of 20000 L / min through a vacuum pipe having an inner diameter of 50 mm and a length of 2 m, the pressure in the vacuum chamber is about 160 Pa (about 1.2 Torr). . At this time, if the dimensions of the annular member 926 and the annular groove of the differential exhaust mechanism are set as shown in FIG. 38, the pressure in the charged beam irradiation space 930 is set to 10 ⁻⁴ Pa (10 ⁻⁶ Torr). be able to.

In FIG. 39, another embodiment of the XY stage is shown. A dry vacuum pump 953 is connected to the vacuum chamber C defined by the housing 98 via vacuum pipes 974 and 975. The annular groove 927 of the differential exhaust mechanism 925 is connected to a turbo molecular pump 951 that is an ultra-high vacuum pump via a vacuum pipe 970 connected to the exhaust port 928. Further, a turbo molecular pump 952 is connected to the inside of the lens barrel 71 via a vacuum pipe 971 connected to the exhaust port 710. These turbo molecular pumps 951 and 952 are connected to a dry vacuum pump 953 by vacuum pipes 972 and 973. (In this figure, the roughing pump of the turbo molecular pump and the vacuum exhaust pump of the vacuum chamber are combined with one dry vacuum pump. However, the flow rate of the high-pressure gas supplied to the static pressure bearing of the XY stage, the volume of the vacuum chamber Depending on the internal surface area and the inner diameter and length of the vacuum pipe, it may be possible to exhaust them with a separate dry vacuum pump.)
A high-purity inert gas (N 2 gas, Ar gas, etc.) is supplied to the static pressure bearing of the XY stage 93 through the flexible pipes 921 and 922. These gas molecules ejected from the hydrostatic bearing diffuse into the vacuum chamber and are exhausted by the dry vacuum pump 953 through the exhaust ports 919, 920a, and 920b. Further, these gas molecules that have entered the differential pumping mechanism and the charged beam irradiation space are sucked from the annular groove 927 or the tip of the lens barrel 71 and exhausted by the turbo molecular pumps 951 and 952 through the exhaust ports 928 and 710. After being discharged from the turbo molecular pump, it is exhausted by the dry vacuum pump 953.

  Thus, the high purity inert gas supplied to the static pressure bearing is collected by the dry vacuum pump and discharged.

  On the other hand, the exhaust port of the dry vacuum pump 953 is connected to the compressor 954 via a pipe 976, and the exhaust port of the compressor 954 is connected to the flexible pipes 931 and 932 via pipes 977, 978 and 979 and regulators 961 and 962. It is connected. For this reason, the high purity inert gas discharged from the dry vacuum pump 953 is pressurized again by the compressor 954 and adjusted to an appropriate pressure by the regulators 961 and 962, and then supplied again to the static pressure bearing of the XY table. The

  Since the gas supplied to the hydrostatic bearing needs to be as highly pure as possible and contain as little water and oil as possible, turbo molecular pumps, dry pumps, and compressors have gas flow paths. It is required to have a structure in which moisture and oil are not mixed. In addition, a cold trap, a filter, etc. (960) are provided in the middle of the discharge side piping 977 of the compressor to trap impurities such as moisture and oil mixed in the circulating gas so that they are not supplied to the static pressure bearing. It is also effective.

  By doing so, the high purity inert gas can be circulated and reused, so that the high purity inert gas can be saved and the inert gas is not spilled into the room where the apparatus is installed. It is possible to eliminate the risk of accidents such as suffocation.

  Note that a high-purity inert gas supply system 963 is connected to the circulation pipe system, and all circulation including the vacuum chamber C, the vacuum pipes 970 to 975, and the pressure side pipes 976 to 980 are started when gas circulation is started. It plays the role of filling the system with high purity inert gas and supplying the shortage when the flow rate of the circulating gas decreases for some reason.

  Further, by providing the dry vacuum pump 953 with a function of compressing to the atmospheric pressure or higher, the dry vacuum pump 953 and the compressor 954 can be combined with one pump.

Furthermore, it is also possible to use a pump such as an ion pump or a getter pump instead of the turbo molecular pump for the ultra-high vacuum pump used for exhausting the lens barrel. However, when these reservoir pumps are used,
In this part, a circulation piping system cannot be constructed. Of course, other types of dry pumps such as a diaphragm type dry pump can be used instead of the dry vacuum pump.

  In FIG. 40, the optical system and detector of the charged beam apparatus according to the present embodiment are schematically shown. Although the optical system is provided in the lens barrel 71, the optical system and the detector are merely examples, and any optical system and detector can be used as necessary. The optical system 760 of the charged beam apparatus includes a primary optical system 72 that irradiates the sample W placed on the stage 50 with a charged beam, a secondary optical system 74 into which secondary electrons emitted from the sample are input, It has. The primary optical system 72 includes an electron gun 721 that emits a charged beam, a lens system 722 that includes a two-stage electrostatic lens that focuses the charged beam emitted from the electron gun 721, a deflector 730, and a charged beam. A Wien filter or E × B separator 723 that deflects the optical axis to be perpendicular to the surface of interest, and a lens system 724 that consists of a two-stage electrostatic lens, as shown in FIG. In order with the electron gun 721 at the top, the optical axis of the charged beam is arranged so as to be inclined with respect to a line perpendicular to the surface (sample surface) of the sample W. The E × B deflector 723 includes an electrode 723-1 and a magnet 723-2.

  The secondary optical system 74 is an optical system into which secondary electrons emitted from the sample W are input, and a lens system composed of a two-stage electrostatic lens disposed above the E × B type deflector 723 of the primary optical system. 741. The detector 761 detects secondary electrons sent through the secondary optical system 74. Since the structure and function of each component of the optical system 760 and the detector 761 are the same as those of the conventional one, detailed description thereof will be omitted.

  The charged beam emitted from the electron gun 721 is shaped by the square opening of the electron gun, is reduced by the two-stage lens system 722, the optical axis is adjusted by the polarizer 730, and the deflection center plane of the E × B deflector 723 is obtained. The image is formed into a square with one side of 1.925 mm. The E × B deflector 723 has a structure in which the electric field and the magnetic field are orthogonal to each other in a plane perpendicular to the normal line of the sample. When the relationship between the electric field, the magnetic field, and the electron energy satisfies a certain condition, the E × B deflector 723 In other cases, the electric field, the magnetic field, and the energy of the electric field are mutually deflected in a predetermined direction. In FIG. 40, the charged beam from the electron gun is incident on the sample W perpendicularly, and the secondary electrons emitted from the sample are set to travel straight in the direction of the detector 761. The shaped beam deflected by the E × B polarizer is reduced to 1/5 by the lens system 724 and projected onto the sample W. The secondary electrons having the pattern image information emitted from the sample W are magnified by the lens systems 724 and 741, and a secondary electron image is formed by the detector 761. This four-stage magnifying lens is a distortion-free lens because the lens system 724 forms a symmetric tablet lens and the lens system 741 also forms a symmetric tablet lens.

According to the present embodiment, the following effects can be obtained.
(B) Using a stage having a structure similar to that of a static pressure bearing type stage generally used in the atmosphere (a stage supporting a static pressure bearing that does not have a differential pumping mechanism) Processing with a charged beam can be performed stably.
(B) It is possible to minimize the influence of the charged beam irradiation area on the degree of vacuum, and it is possible to stabilize the processing of the sample by the charged beam.
(C) It is possible to provide an inspection apparatus with high accuracy in positioning the stage and a stable degree of vacuum in the charged beam irradiation area.
(D) It is possible to provide an exposure apparatus with high accuracy in stage positioning performance and a stable vacuum degree in the charged beam irradiation area at low cost.
(E) A fine semiconductor circuit can be formed by manufacturing a semiconductor with an apparatus in which the stage positioning performance is highly accurate and the degree of vacuum in the charged beam irradiation region is stable.

Modification FIG 41 of the inspection apparatus shows a schematic configuration of a defect inspection apparatus according to a modification of the present invention.
This defect inspection apparatus is the above-described projection type inspection apparatus, which is an electron gun 721 that emits a primary electron beam, an electrostatic lens 722 that deflects and shapes the emitted primary electron beam, and an electric field that is formed from the primary electron beam. An E × B deflector 723 that deflects the semiconductor wafer W so as to be substantially perpendicular to the field perpendicular to E and the magnetic field B, an objective lens 724 that forms an image of the deflected primary electron beam on the wafer W, and can be evacuated to a vacuum. A stage 50 that is provided in a sample chamber (not shown) and is movable in a horizontal plane with the wafer W placed thereon, and a secondary electron beam and / or a reflected electron beam emitted from the wafer W by irradiation with the primary electron beam An electrostatic lens 741 of a projection system for mapping and projecting at a magnification, a detector 770 for detecting the focused image as a secondary electron image of the wafer, and controlling the entire apparatus. Configured to include a control unit 1016 for executing the processing for detecting defects of the wafer W based on the detected by the detector 770 secondary electronic image. The secondary electron image includes contributions from not only secondary electrons but also scattered electrons and reflected electrons. Here, the secondary electron image is referred to as a secondary electron image.

  Further, between the objective lens 724 and the wafer W, there is interposed a deflection electrode 1011 for deflecting the incident angle of the primary electron beam to the wafer W by an electric field or the like. A deflection controller 1012 that controls the electric field of the deflection electrode 1011 is connected to the deflection electrode 1011. The deflection controller 1012 is connected to the control unit 1016 and controls the deflection electrode so that an electric field corresponding to a command from the control unit 1016 is generated by the deflection electrode 1011. The deflection controller 1012 can be configured as a voltage control device that controls the voltage applied to the deflection electrode 1011.

  The detector 770 can have any configuration as long as the secondary electron image formed by the electrostatic lens 741 can be converted into a post-processable signal. For example, as shown in detail in FIG. 46, the detector 770 includes a multi-channel plate 771, a fluorescent screen 772, a relay optical system 773, and an image sensor 56 composed of a number of CCD elements. be able to. The multi-channel plate 771 has a large number of channels in the plate, and generates a larger number of electrons while the secondary electrons imaged by the electrostatic lens 741 pass through the channel. That is, secondary electrons are amplified. The fluorescent screen 772 converts the secondary electrons into light by emitting fluorescence with the amplified secondary electrons. The relay lens 773 guides this fluorescence to the CCD image sensor 774. The CCD image sensor 774 converts the intensity distribution of the secondary electrons on the surface of the wafer W into an electric signal for each element, that is, digital image data, and outputs it to the control unit 1016. To do.

  As illustrated in FIG. 41, the control unit 1016 can be configured by a general-purpose personal computer or the like. This computer includes a control unit main body 1014 that executes various controls and arithmetic processes according to a predetermined program, a CRT 1015 that displays the processing results of the main body 1014, an input unit 1018 such as a keyboard and a mouse for an operator to input commands, Of course, the control unit 1016 may be configured by hardware dedicated to the defect inspection apparatus, a workstation, or the like.

  The control unit body 1014 includes various control boards such as a CPU, RAM, ROM, hard disk, and video board (not shown). A secondary electron image storage area 1008 for storing the electrical signal received from the detector 770, that is, the digital image data of the secondary electron image of the wafer W, is allocated on a memory such as a RAM or a hard disk. In addition, a reference image storage unit 1013 for storing reference image data of a wafer having no defect in advance exists on the hard disk. Further, on the hard disk, in addition to a control program for controlling the entire defect inspection apparatus, secondary electron image data is read from the storage area 1008, and defects of the wafer W are automatically detected according to a predetermined algorithm based on the image data. A defect detection program 1009 is stored. As will be described in detail later, the defect detection program 1009 automatically detects a defective portion by matching the reference image read from the reference image storage unit 1013 with the actually detected secondary electron beam image. When it is determined that there is a defect, it has a function of displaying a warning to the operator. At this time, the secondary electron image 1017 may be displayed on the display unit of the CRT 1015.

  Next, the operation of the defect inspection apparatus according to this embodiment will be described with reference to the flowcharts of FIGS.

  First, as shown in the flow of the main routine in FIG. 43, the wafer W to be inspected is set on the stage 50 (step 1300). As described above, all the wafers stored in the loader may be automatically set on the stage 50 one by one.

  Next, images of a plurality of regions to be inspected that are displaced from each other while partially overlapping each other on the XY plane of the surface of the wafer W are acquired (step 1304). As shown in FIG. 47, the plurality of inspected regions to be acquired are, for example, reference numbers 1032a, 1032b,. . . 1032k,. . . It can be seen that the positions are shifted while partially overlapping around the inspection pattern 1030 of the wafer. For example, as shown in FIG. 42, 16 images 1032 (inspected images) of the inspected region are acquired. Here, in the image shown in FIG. 42, a rectangular cell corresponds to one pixel (or a block unit larger than the pixel), and a black cell corresponds to an image portion of a pattern on the wafer W. Details of step 1304 will be described later with reference to the flowchart of FIG.

  Next, the image data of the plurality of regions to be inspected acquired in step 1304 is compared with the reference image data stored in the storage unit 1013 (step 1308 in FIG. 43), and is covered by the plurality of regions to be inspected. It is determined whether there is a defect on the wafer inspection surface. In this step, so-called image data matching processing is executed. Details thereof will be described later with reference to the flowchart of FIG.

  If it is determined from the comparison result in step 1308 that there is a defect in the wafer inspection surface covered by the plurality of inspection regions (Yes in step 1312), the operator is warned of the presence of the defect (step 1318). As a warning method, for example, a message notifying the presence of a defect may be displayed on the display unit of the CRT 1015, or at the same time, an enlarged image 1017 of a pattern having a defect may be displayed. Such a defective wafer may be immediately taken out from the sample chamber 31 and stored in a storage place different from the wafer having no defect (step 1319).

  As a result of the comparison processing in step 1308, when it is determined that the wafer W is free of defects (No in step 1312), it is determined whether or not there is still an area to be inspected for the wafer W currently inspected. (Step 1314). When the area to be inspected remains (Yes in Step 1314), the stage 50 is driven, and the wafer W is moved so that the other area to be inspected now falls within the irradiation area of the primary electron beam (Step 1316). . Thereafter, the process returns to step 1302 and the same processing is repeated for the other inspection regions.

  If the area to be inspected does not remain (No in step 1314), or after the defective wafer extraction process (step 1319), whether or not the wafer W currently being inspected is the final wafer, That is, it is determined whether an uninspected wafer remains in a loader (not shown) (step 320). If it is not the final wafer (No in step 1320), the inspected wafer is stored in a predetermined storage location, and a new uninspected wafer is set on the stage 50 instead (step 1322). Thereafter, the process returns to step 1302 and the same processing is repeated for the wafer. If it is the final wafer (Yes at step 1320), the inspected wafer is stored in a predetermined storage location, and the entire process is completed.

  Next, the processing flow of step 1304 will be described with reference to the flowchart of FIG.

In FIG. 44, first, the image number i is set to the initial value 1 (step 1330). This image number is an identification number sequentially assigned to each of the plurality of inspection area images. Next, the image position (X _i , Y _i ) is determined for the set inspection area of image number i (step 1332). This image position is defined as a specific position in the area for defining the inspection area, for example, a center position in the area. At this time, since i = 1, the image position (X ₁ , Y ₁ ) is obtained, which corresponds to the center position of the inspection area 1032a shown in FIG. 47, for example. The image positions of all the image areas to be inspected are determined in advance, for example, stored on the hard disk of the control unit 1016 and read out in step 1332.

Next, the deflection controller 1012 causes the deflecting electrode 1011 to pass through the deflecting electrode 1011 of FIG. 41 so that the image area to be inspected at the image position (X _i , Y _i ) determined in step 1332 is irradiated. A potential is applied to 1011 (step 1334 in FIG. 44).

Next, a primary electron beam is emitted from the electron gun 721 and irradiated onto the set wafer W surface through the electrostatic lens 722, the E × B deflector 723, the objective lens 724, and the deflection electrode 1011 (step 1336). At this time, the primary electron beam is deflected by the electric field generated by the deflection electrode 1011 and irradiated over the entire image area to be inspected at the image position (X _i , Y _i ) on the wafer inspection surface 1034. When the image number i = 1, the area to be inspected is 1032a.

  Secondary electrons and / or reflected electrons (hereinafter referred to as “secondary electrons” only) are emitted from the region to be inspected irradiated with the primary electron beam. Therefore, the generated secondary electron beam is imaged on the detector 770 at a predetermined magnification by the electrostatic lens 741 of the magnification projection system. The detector 770 detects the imaged secondary electron beam and converts it into an electrical signal for each detection element, that is, digital image data (step 1338). Then, the detected digital image data of the image number i is transferred to the secondary electronic image storage area 8 (step 1340).

Next, the image number i is incremented by 1 (step 1342), it determines whether the incremented image number (i + 1) exceeds the fixed value i _MAX (step 1344). This i _MAX is the number of inspected images to be acquired, and is “16” in the above example of FIG.

When the image number i does not exceed the predetermined value i _MAX (No determination at Step 1344), the process returns to Step 1332 again, and the image position (X _{i + 1} , Y _{i + 1} ) is determined again for the incremented image number (i + 1). To do. This image position is a position moved from the image position (X _i , Y _i ) determined in the previous routine by a predetermined distance (ΔX _i , ΔY _i ) in the X direction and / or Y direction. In the example of FIG. 41, the inspected area is a position (X ₂ , Y ₂ ) moved only in the Y direction from (X ₁ , Y ₁ ), and becomes a rectangular area 1032b indicated by a broken line. It should be noted that the value of (ΔX _i , ΔY _i ) (i = 1, 2,... I _MAX ) indicates how much the pattern 1030 on the wafer inspection surface 1034 actually deviates from the field of view of the detector 770 empirically. It can be appropriately determined from the data and the number and area of the areas to be inspected.

Then, the processes in steps 1332 to 1342 are sequentially repeated for i _MAX areas to be inspected. As shown in FIG. 47, these inspected regions partially overlap on the inspection surface 1034 of the wafer so that the inspected image region 1032k is obtained at the image position (X _k , Y _k ) moved k times. However, the position is shifted. In this way, the 16 pieces of inspected image data illustrated in FIG. 42 are acquired in the image storage area 1008. As shown in FIG. 42, the acquired images 1032 (inspected images) of the plurality of inspected regions partially or completely capture the image 1030 a of the pattern 1030 on the wafer inspection surface 1034.

If the incremented image number i exceeds i _MAX (YES at step 1344), the subroutine is returned to and the process proceeds to the main routine comparison step (step 308) in FIG.

  Note that the image data transferred to the memory in step 1340 is composed of secondary electron intensity values (so-called solid data) for each pixel detected by the detector 770, but a subsequent comparison step (step 1308 in FIG. 37). Since the matching calculation is performed with the reference image, it can be stored in the storage area 1008 in a state where various calculation processes are performed. Such arithmetic processing includes, for example, normalization processing for matching the size and / or density of the image data with the size and / or density of the reference image data, and an isolated pixel group having a predetermined number of pixels or less as noise. There is a process to remove. Furthermore, instead of simple solid data, the data may be compressed and converted into a feature matrix in which the features of the detection pattern are extracted within a range that does not reduce the detection accuracy of the high-definition pattern. As such a feature matrix, for example, a two-dimensional inspection area composed of M × N pixels is divided into m × n (m <M, n <N) blocks, and secondary electrons of the pixels included in each block. There is an m × n feature matrix or the like in which the sum of intensity values (or a normalized value obtained by dividing this sum by the total number of pixels in the entire region to be inspected) is used as each matrix component. In this case, the reference image data is also stored in the same expression. The image data referred to in the embodiment of the present invention includes not only simple data but also image data whose features are extracted by an arbitrary algorithm.

  Next, the processing flow of step 1308 will be described with reference to the flowchart of FIG.

  First, the CPU of the control unit 1016 reads reference image data from a reference image storage unit 1013 (FIG. 41) onto a working memory such as a RAM (step 1350). This reference image is represented by reference numeral 1036 in FIG. Then, the image number i is reset to 1 (step 1352), and the inspected image data of the image number i is read from the storage area 1008 onto the working memory (step 1354).

Next, the read reference image data and image i data are matched to calculate a distance value D _i between them (step 1356). This distance value D _i represents the similarity between the reference image and the inspected image i, and the greater the distance value, the greater the difference between the reference image and the inspected image. Any value can be used as long as the distance value D _i represents the similarity. For example, when the image data is composed of M × N pixels, the secondary electron intensity (or feature amount) of each pixel is regarded as each position vector component in the M × N dimensional space, and the reference image vector in this M × N dimensional space. And the Euclidean distance or correlation coefficient between the image i vectors. Of course, a distance other than the Euclidean distance, such as a so-called city area distance, can also be calculated. Furthermore, since the amount of calculation becomes enormous when the number of pixels is large, the distance value between the image data represented by the m × n feature vector may be calculated as described above.

Next, it is determined whether or not the calculated distance value D _i is smaller than a predetermined threshold Th (step 1358). This threshold value Th is experimentally obtained as a reference for determining a sufficient match between the reference image and the image to be inspected.

When the distance value D _i is smaller than the predetermined threshold Th (Yes in Step 1358), it is determined that there is no defect on the inspection surface 1034 of the wafer W (Step 1360), and this subroutine is returned. That is, if at least one of the images to be inspected substantially matches the reference image, it is determined that there is no defect. Thus, since it is not necessary to perform matching with all the images to be inspected, high-speed determination is possible. In the example of FIG. 42, it can be seen that the image to be inspected in the third row and the third column is substantially coincident with the reference image with no positional deviation.

When the distance value D _i is equal to or larger than the predetermined threshold Th (No at Step 1358), the image number i is incremented by 1 (Step 1362), and whether or not the incremented image number (i + 1) exceeds a certain value i _MAX . Is determined (step 1364).

When the image number i does not exceed the predetermined value i _MAX (No determination at Step 1364), the process returns to Step 1354 again, image data is read for the incremented image number (i + 1), and the same processing is repeated.

If the image number i exceeds a certain value i _MAX (Yes at Step 1364), it is determined that the inspection surface 1034 of the wafer W is “defect” (Step 1366), and this subroutine is returned. That is, if all of the inspected images do not substantially match the reference image, it is determined that “there is a defect”.

  Although the above is each embodiment of a stage apparatus, this invention is not limited only to the said example, It can change arbitrarily suitably within the scope of the summary of this invention.

  For example, the semiconductor wafer W is taken as an example of the sample to be inspected, but the sample to be inspected according to the present invention is not limited to this, and any one that can detect a defect with an electron beam can be selected. For example, a mask or the like on which a pattern for exposing a wafer is formed can be an inspection target.

  Further, the present invention can be applied not only to an apparatus that performs defect detection using a charged particle beam other than electrons, but also to an arbitrary apparatus that can acquire an image capable of inspecting a defect of a sample.

Furthermore, the deflection electrode 1011 can be placed not only between the objective lens 724 and the wafer W but also at an arbitrary position as long as the irradiation region of the primary electron beam can be changed. For example, there are between the E × B deflector 723 and the objective lens 724 and between the electron gun 721 and the E × B deflector 723. Furthermore, the deflection direction may be controlled by controlling the field generated by the E × B deflector 723. That is, the function of the deflection electrode 1011 may be combined with the E × B deflector 723.

Further, in the above-described embodiment, when matching image data, either pixel matching or feature vector matching is used. However, both may be combined. For example, first, high-speed matching is performed using feature vectors with a small amount of calculation, and as a result, for a high-similarity image to be inspected, matching is performed with more detailed pixel data, thereby achieving high speed and accuracy. Can be made compatible.

  In the embodiment of the present invention, the position shift of the image to be inspected is handled only by the position shift of the irradiation region of the primary electron beam, but the process of searching for the optimum matching area on the image data before or during the matching process ( For example, a region having a high correlation coefficient is detected and matched) and the present invention can be combined. According to this, a large positional shift of the image to be inspected can be dealt with by the positional shift of the irradiation region of the primary electron beam according to the present invention, and a relatively small positional shift can be absorbed by the subsequent digital image processing. The accuracy of detection can be improved.

  Furthermore, although the configuration of FIG. 41 is shown as the electron beam apparatus for defect inspection, the electron optical system and the like can be arbitrarily changed. For example, the electron beam irradiation means (721, 722, 723) of the defect inspection apparatus shown in FIG. 41 is a type in which the primary electron beam is incident on the surface of the wafer W from vertically above, but the E × B deflection. The vessel 723 may be omitted, and the primary electron beam may be incident on the surface of the wafer W obliquely.

  Further, the flow of the flowchart of FIG. 43 is not limited to this. For example, the sample determined to be defective in step 1312 is not subjected to defect inspection in other areas, but the processing flow may be changed so as to detect defects covering the entire area. Further, if the irradiation region of the primary electron beam can be expanded and almost the entire inspection region of the sample can be covered by one irradiation, Step 1314 and Step 1316 can be omitted.

  As described above in detail, according to the defect inspection apparatus of the present embodiment, images of a plurality of inspection areas displaced from each other while partially overlapping on the sample are obtained, and images of these inspection areas are obtained. By comparing the reference image with the reference image, the defect of the sample is inspected. Therefore, it is possible to obtain an excellent effect that the deterioration of the defect inspection accuracy due to the positional deviation between the image to be inspected and the reference image can be prevented.

Furthermore, according to the device manufacturing method of the present invention, since the defect inspection of the sample is performed using the defect inspection apparatus as described above, it is possible to improve the yield of products and prevent the shipment of defective products. Is obtained.

Another embodiment of the electron beam apparatus Further, considering another solution of the problem of the mapping projection method, there is a plurality of primary electron beams, and the plurality of electron beams are scanned two-dimensionally (XY direction). However, (raster scan) irradiates the observation area on the sample surface, and the secondary electron optical system employs a mapping projection method. This method has the advantages of the above-mentioned mapping projection method, and is a problem of this mapping method (1) It is easy to charge up on the sample surface to irradiate the electron beam at a time, (2) With this method The fact that the obtained electron beam current has a limit (about 1.6 μA) and hinders the improvement of the inspection speed can be solved by scanning a plurality of electron beams. That is, since the electron beam irradiation point moves, the charge easily escapes and the charge-up is reduced. Further, the current value can be easily increased by increasing the number of the plurality of electron beams. In the embodiment, when four electron beams are used, a total of 2 μA is obtained with one electron beam current of 500 nA (electron beam diameter 10 μm). The number of electron beams can be easily increased to about 16, and in this case, 8 μA can be obtained in principle. The scanning of a plurality of electron beams only needs to be performed so that the irradiation amount of the plurality of electron beams is uniform in the irradiation region. Therefore, scanning of other shapes such as a Lissajous figure is not limited to the raster scanning as described above. It may be in shape. Therefore, the scanning direction of the stage need not be perpendicular to the scanning direction of the plurality of electron beams.
Electron gun (electron beam source)
A thermal electron beam source is used as the electron beam source used in this embodiment. Electron emission (emitter) material is LaB _6. Other materials can be used as long as the material has a high melting point (low vapor pressure at high temperature) and a small work function. Two methods are used to obtain a plurality of electron beams. One is a method of obtaining a plurality of electron beams by drawing one electron beam from one emitter (one protrusion) and passing a thin plate (open plate) with a plurality of holes, and the other method is In this method, a plurality of protrusions are formed on a single emitter, and a plurality of electron beams are drawn directly therefrom. In either case, the electron beam utilizes the property of being easily emitted from the tip of the protrusion. Other types of electron beam sources such as thermal field emission type electron beams can also be used.

  The thermoelectron beam source is a system that emits electrons by heating the electron emission material. The thermoelectrolytic emission electron beam source emits electrons by applying a high electric field to the electron emission material. This is a system in which electron emission is stabilized by heating the emission part.

  FIG. 48A is a schematic view of an electron beam apparatus according to another embodiment. On the other hand, FIG. 48B is a schematic plan view showing an aspect in which a sample is scanned with a plurality of primary electron beams. The electron gun 721 operable under the space charge limiting condition forms a multi-beam as indicated by reference numeral 711 in FIG. 48B. The multi-beam 711 is composed of primary electron beams 711a which are eight circular beams arranged on the circumference.

  A plurality of primary electron beams 711a generated by the electron gun 721 are focused using lenses 722-1 and 722-2, and are applied to the sample W by an E × B separator 723 including an electrode 723-1 and a magnet 723-2. So that it is incident at a right angle. A multi-beam 711 comprising a plurality of primary electromagnetic rays 711a focused on the sample W by a primary optical system including these elements 711, 722-1, 722-2, 723, a lens 724-1 and an objective lens 724-2. Is used for scanning on the sample W by a two-stage deflector (not shown; included in the primary optical system) provided downstream of the lens 722-2.

  The scanning of the sample W is performed in the x-axis direction with the main surface of the objective lens 724-2 as the center of deflection. As shown in FIG. 48B, the primary electron beams 711a of the multi-beams 711 are arranged apart from each other on the circumference, and are adjacent to each other when projected onto the y-axis orthogonal to the x direction that is the scanning direction. The distance between the primary electron beams 711a (measured at the center of each primary electron beam) is designed to be equal. At this time, the primary electron beams 711a adjacent to each other may be separated from each other, may be in contact with each other, or may be partially overlapped.

  As shown in FIG. 48B, since the primary electron beams 711a constituting the multi-beam 711 are arranged apart from each other, the current density limit value of each primary electron beam 711a, that is, the sample W is not charged. The limit current density value can be maintained equivalent to the case where a single circular beam is used, thereby preventing a reduction in the S / N ratio. Further, since the primary electron beams 711a are separated from each other, the space charge effect is small.

  On the other hand, the multi-beam 711 can scan the sample W at a uniform density over the entire surface of the field of view 713 by a single scan. Thereby, an image can be formed with high throughput, and the inspection time can be shortened. In FIG. 48B, if reference numeral 711 indicates a multi-beam at the start point of scanning, reference numeral 711a indicates a multi-beam at the end point of scanning.

  The sample W is placed on a sample table (not shown). This stage is continuously moved along a direction y orthogonal to the scanning direction x during scanning in the x direction (for example, scanning with a width of 200 μm). Thereby, raster scanning is performed. A driving device (not shown) for moving the stage on which the sample is placed is provided.

  Secondary electrons generated from the sample W during scanning and emitted in various directions are accelerated in the optical axis direction by the objective lens 724-2. As a result, secondary electrons emitted from various points in various directions are respectively Are converged finely, and the distance between the images is enlarged by the lenses 724-1, 741-1, and 741-2. A secondary electron beam 712 formed through a secondary optical system including these lenses 724-1, 724-2, 741-1 and 741-2 is projected onto the light receiving surface of the detector 761, and an enlarged image of the field of view. Is imaged.

  A detector 761 included in the optical optical system multiplies the secondary electron beam with an MCP (microchannel plate), converts it into an optical signal with a scintillator, and converts it into an electrical signal with a CCD detector. A two-dimensional image of the sample W can be formed by an electrical signal from the CCD. Each primary electron beam 711a has a size of at least two CCD pixels.

  By operating the electron gun 721 under the space charge limiting condition, the shot noise of the primary electron beam 711a can be reduced by about an order of magnitude compared to when operating under the temperature limiting condition. Therefore, the shot noise of the secondary electron signal can be reduced by an order of magnitude, so that a signal with a good S / N ratio can be obtained.

    According to the electron beam apparatus of the present embodiment, the S / N ratio can be reduced by maintaining the current density limit value of the primary electron beam that does not cause charging of the sample equal to the case where a single circular beam is used. The inspection time can be shortened by forming an image with high throughput while preventing it.

  In addition, the device manufacturing method according to the present embodiment can improve the yield by evaluating the wafer after the completion of each wafer process using the electron beam apparatus.

  FIG. 49A is a diagram showing details of the electron beam apparatus according to the embodiment of FIG. 48A. Four electron beams 711 (711-1, 711-2, 711-3, 711-4) emitted from the electron gun 721 are shaped by the aperture stop NA-1, and two-stage lenses 722-1, 722 are formed. 2 is formed into an elliptical shape of 10 μm × 12 μm on the deflection center plane of the Wien filter 723, and is raster-scanned by the deflector 730 in the direction perpendicular to the paper surface of the figure, and a rectangular area of 1 mm × 0.25 mm as a whole of the four electron beams The image is formed so as to cover uniformly. A plurality of electron beams deflected by EXB 723 are crossed over by an NA aperture, reduced to 1/5 by a lens 724, and 200 μ × 50 μm is covered on the sample W, and irradiated and projected so as to be perpendicular to the sample surface (Called Kohler lighting). Four secondary electron beams 712 having information of a pattern image (sample image F) emitted from the sample are expanded by lenses 724, 741-1, and 741-2, and four electron beams as a whole on the MCP767. An image is formed as a rectangular image (enlarged projection image F ′) synthesized at 712. The enlarged projection image F ′ by the secondary electric line 712 is sensitized 10,000 times by the MCP 767, converted into light by the fluorescent unit 767, and becomes an electric signal synchronized with the continuous moving speed of the sample by the TDI-CCD 762. The images are acquired as continuous images by the image display unit 765 and output on the CRT or the like.

  The electron beam irradiation unit needs to irradiate the sample surface with the electron beam in a rectangular or elliptical shape with as little uniformity as possible and with less irradiation unevenness. Irradiation is necessary. Conventional non-uniformity of electron beam irradiation is about ± 10%, and the non-uniformity of image contrast is large. Further, since the electron beam irradiation current is as small as about 500 nA in the irradiation region, there is a problem that high throughput cannot be obtained. In addition, compared with the scanning electron microscope (SEM) method, this method has a problem in that an image formation failure due to charge-up is likely to occur because a large image observation area is collectively irradiated with an electron beam.

  The primary electron beam irradiation method of this example is shown in FIG. 49B. The primary electron beam 711 is composed of four electron beams 711-1, 711-2, 711-3, and 711-4, and each beam has an elliptical shape of 2 μm × 2.4 μm, and each beam is 200 μm. Raster scan is performed on a rectangular area of 12.5 μm, and they are added so that they do not overlap, and a rectangular area of 200 μx50 μm is irradiated as a whole. The beam of 711-1 arrives at 711-1 'in a finite time, and then returns to the point immediately below 711-1 (202 direction) shifted by the beam spot diameter (10 μm) with almost no time loss. In this time, it moves in parallel to 711-1 to 711-1 ′ and directly below 711-1 ′ (in the 711-2 ′ direction), and this is repeated until the rectangular irradiation area indicated by the dotted line in the figure is ¼ (200 μm). After scanning 12.5 μm), the process returns to the first point 711-1 and is repeated at high speed. The other electron beams 711-2 to 711-4 are repeatedly scanned at the same speed as the electron beam 711-1 and irradiate the rectangular irradiation region (200 μ × 50 μm) as a whole at high speed uniformly. As long as the irradiation can be performed uniformly, the raster scan may not be performed. For example, scanning may be performed so as to draw a Lissajous shape. Therefore, the moving direction of the stage need not be the direction A shown in the figure. That is, it is not necessary to be perpendicular to the scanning direction (the high-speed scanning direction in the horizontal direction in the figure). In this example, unevenness of electron beam irradiation could be performed at about ± 3%. The irradiation current was 250 nA per electron beam, and 1.0 μA was obtained with four electron beams as a whole on the sample surface (twice as compared with the conventional method). By increasing the number of electron beams, current can be increased and high throughput can be obtained. Further, since the irradiation point is smaller than the conventional one (about 1/80 in area) and moved, the charge-up can be suppressed to 1/20 or less of the conventional one.

Although not shown in the figure, in addition to the lens, this apparatus includes a limited field stop, a deflector (aligner) having four or more poles for adjusting the axis of the electron beam, astigmatism. A unit necessary for illumination and imaging of an electron beam such as a corrector (stigmator) and a plurality of quadrupole lenses (quadrupole lenses) for shaping the beam shape are provided.
Device Manufacturing Method Next, an embodiment of a semiconductor device manufacturing method according to the present invention will be described with reference to FIGS.

FIG. 50 is a flowchart showing an embodiment of a semiconductor device manufacturing method according to the present invention. The manufacturing process of this embodiment includes the following main processes.
(1) Wafer manufacturing process for manufacturing a wafer (or wafer preparation process for preparing a wafer) (Step 1400)
(2) A mask manufacturing process for manufacturing a mask used for exposure (or a mask preparing process for preparing a mask) (step 1401)
(3) Wafer processing process for performing necessary processing on the wafer (step 1402)
(4) Chip assembly process for cutting out chips formed on the wafer one by one and making them operable (step 1403)
(5) Chip inspection process for inspecting the completed chip (step 1404)
Each of the main processes described above further includes several sub-processes.

Among these main processes, the wafer processing process (3) has a decisive influence on the performance of the semiconductor device. In this step, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as memories and MPUs. This wafer processing step includes the following steps.
(A) A thin film forming process for forming a dielectric thin film to be an insulating layer, a wiring portion, or a metal thin film for forming an electrode portion (using CVD, sputtering, etc.)
(B) Oxidation process for oxidizing the thin film layer and wafer substrate (C) Lithography process for forming a resist pattern using a mask (reticle) to selectively process the thin film layer and wafer substrate, etc. (D) Resist pattern Etching process (eg using dry etching technology) to process thin film layers and substrates according to
(E) Ion / impurity implantation / diffusion process (F) Resist stripping process (G) Process for inspecting the processed wafer The wafer processing process is repeated as many times as necessary to manufacture a semiconductor device that operates as designed.

FIG. 51A is a flowchart showing a lithography process that is the core of the wafer processing process of FIG. This lithography process includes the following steps.
(A) A resist coating process for coating a resist on the wafer on which the circuit pattern is formed in the preceding process (step 1500).
(B) Step of exposing the resist (Step 1501)
(C) Development process of developing the exposed resist to obtain a resist pattern (step 1502)
(D) An annealing step for stabilizing the developed resist pattern (step 1503)
The semiconductor device manufacturing process, wafer processing process, and lithography process are well known and need no further explanation.

When the defect inspection method and the defect inspection apparatus according to the present invention are used in the inspection step (G), even a semiconductor device having a fine pattern can be inspected with high throughput, so that 100% inspection is possible, and the yield of products is improved. It becomes possible to prevent shipment of defective products.

Inspection Procedure An inspection procedure in the inspection step (G) will be described.

  In general, a defect inspection apparatus using an electron beam is expensive and has a lower throughput than other process apparatuses. Therefore, an important process (e.g., etching, film formation, or CMP (Chemical Mechanical Polishing) flattening process, etc.).

The wafer to be inspected is positioned on the ultra-precise XY stage through the atmospheric transfer system and the vacuum transfer system, and then fixed by the electrostatic chuck mechanism, etc., and thereafter defect inspection is performed according to the procedure of FIG. 51B. . First, as necessary, the position of each die is confirmed and the height of each location is detected and stored by an optical microscope. In addition to this, the optical microscope acquires an optical microscope image of a desired location such as a defect and is used for comparison with an electron beam image. Next, recipe information according to the type of wafer (after which process, the wafer size is 20 cm or 30 cm, etc.) is input to the apparatus, and then the inspection location designation, electron optical system setting, inspection condition setting, etc. After performing the above, defect inspection is normally performed in real time while acquiring an image. Cell-to-cell comparison, die comparison, and the like are inspected by a high-speed information processing system equipped with an algorithm, and the results are output to a CRT or stored in a memory as necessary. Defects include particle defects, shape abnormalities (pattern defects), and electrical (disconnections such as wiring or vias and poor conduction) defects, etc., which can be distinguished from each other, the size of the defect, and killer defects (the use of chips). It is also possible to automatically classify critical defects that are impossible) in real time. Detection of an electrical defect is achieved by detecting a contrast abnormality. For example, a place with poor conduction is normally positively charged by electron beam irradiation (about 500 eV), and the contrast is lowered, so that it can be distinguished from a normal place. The electron beam irradiation means in this case is a low potential (energy) electron beam generation means (thermoelectron generation, UV / photoelectron) provided to make contrast due to potential difference stand out separately from the electron beam irradiation means for normal inspection. ). Before irradiating the inspection target region with the electron beam for inspection, this low potential (energy) electron beam is generated and irradiated. In the case of a projection method that can be positively charged by irradiating an inspection electron beam, it is not necessary to provide a low-potential electron beam generating means depending on the specifications. Further, it is possible to detect a defect from a difference in contrast caused by applying a positive or negative potential to a sample such as a wafer with respect to a reference potential (which occurs because the flowability varies depending on the forward direction or reverse direction of the element). It can also be used for line width measurement equipment and alignment accuracy measurement.

FIG. 1 is an elevational view showing the main components of the inspection apparatus according to the present invention, as viewed along line AA in FIG. 2A is a plan view of the main components of the inspection apparatus shown in FIG. 1 and is a view taken along line BB in FIG. FIG. 2B is a schematic sectional view showing another embodiment of the substrate carrying-in apparatus according to the present invention. FIG. 3 is a cross-sectional view of the mini-environment device of FIG. 1 as viewed along line CC. 4 is a view showing the loader housing of FIG. 1 as viewed along line DD in FIG. FIG. 5 is an enlarged view of the wafer rack, where [A] is a side view and [B] is a cross-sectional view taken along line EE of [A]. FIG. 6 is a view showing a modification of the method for supporting the main housing. FIG. 7 is a view showing a modification of the method for supporting the main housing. FIG. 8 is a schematic diagram showing a schematic configuration of the electron optical device of the inspection apparatus of FIG. FIG. 9 is a cross-sectional view showing the structure of the electron beam deflection unit of the EXB separator. 10 is a cross-sectional view taken along line AA in FIG. FIG. 11 is an overall configuration diagram for explaining an embodiment apparatus of the present invention. FIG. 12 is a perspective view of an electrode, and is a perspective view illustrating a case where the electrode is cylindrically symmetrical with respect to an axis. FIG. 13 is a perspective view of the electrode, and is a perspective view showing a case where the electrode has an axisymmetric disk shape. FIG. 14 is a graph showing a voltage distribution between the wafer and the objective lens. FIG. 15 is a flowchart showing the secondary electron detection operation of the electron beam apparatus. FIG. 16 is a cross-sectional view of the E × B separator of the present invention. FIG. 17 is a diagram showing the electric field distribution of the E × B separator of the present invention. FIG. 18 is a schematic configuration diagram showing a main part of an embodiment of the precharge unit according to the present invention. FIG. 19 is a schematic configuration diagram showing another embodiment of the precharge unit. FIG. 20 is a schematic configuration diagram showing still another embodiment of the precharge unit. FIG. 21 is a schematic configuration diagram showing still another embodiment of the precharge unit. FIG. 22 is a schematic diagram of one embodiment of an imaging apparatus according to the present invention. FIG. 23 is a diagram illustrating the operation timing for equalizing or reducing the electric charge charged in the target of the imaging apparatus of FIG. FIG. 24 is a schematic configuration diagram of a defect inspection apparatus including a precharge unit according to another embodiment of the present invention. FIG. 25 is a schematic configuration diagram of a defect inspection apparatus including a precharge unit according to another embodiment of the present invention. FIG. 26 is a schematic configuration diagram of a defect inspection apparatus including a precharge unit according to still another embodiment of the present invention. FIG. 27 is a flowchart showing a wafer inspection flow of the defect inspection apparatus according to the embodiment shown in FIGS. FIG. 28 is a diagram for explaining a specific example of a wafer defect detection method in the defect inspection apparatus according to the embodiment of FIGS. 24 to 26, where (a) shows pattern defect detection and (b) shows line width. Measurement (c) shows potential contrast measurement. FIG. 29 is a diagram showing a potential application mechanism. FIG. 30 is a diagram for explaining the electron beam calibration mechanism, [A] is a side view, and [B] is a plan view. FIG. 31 is a schematic explanatory diagram of a wafer alignment control apparatus. FIG. 32 is a view showing a vacuum chamber and an XY stage of an embodiment of the charged beam apparatus of the present invention, wherein [A] is a front view and [B] is a side view. FIG. 33 is a diagram showing a vacuum chamber and an XY stage according to another embodiment of the charged beam apparatus of the present invention. FIG. 34 is a diagram showing a vacuum chamber and an XY stage of another embodiment of the charged beam apparatus of the present invention. FIG. 35 is a diagram showing a vacuum chamber and an XY stage of still another embodiment of the charged beam apparatus of the present invention. FIG. 36 is a diagram showing a vacuum chamber and an XY stage of still another embodiment of the charged beam apparatus of the present invention. FIG. 37 is a diagram showing a vacuum chamber and an XY stage according to an embodiment of the charged beam apparatus of the present invention. FIG. 38 is a diagram showing an example of an operating exhaust mechanism provided in the apparatus shown in FIG. FIG. 39 is a view showing a gas circulation piping system of the apparatus shown in FIG. FIG. 40 is a schematic diagram illustrating an example of an optical system and a detection system provided in the lens barrel. FIG. 41 is a schematic configuration diagram of a defect inspection apparatus according to a modification of the present invention. FIG. 42 is a diagram illustrating an example of a plurality of inspected images and reference images acquired by the defect inspection apparatus in FIG. FIG. 43 is a flowchart showing the flow of the main routine of wafer inspection in the defect inspection apparatus of FIG. FIG. 44 is a flowchart showing a detailed flow of a subroutine of the plurality of inspected image data acquisition steps (step 1304) in FIG. FIG. 45 is a flowchart showing a detailed flow of a subroutine of the comparison step (step 1308) in FIG. FIG. 46 is a diagram showing a specific configuration example of the detector of the defect inspection apparatus in FIG. FIG. 47 is a diagram conceptually showing a plurality of areas to be inspected whose positions are shifted from each other while partially overlapping on the surface of the semiconductor wafer. FIG. 48A is a schematic view of an electron beam apparatus according to another embodiment of the present invention. FIG. 48B is a schematic plan view showing an aspect in which the sample is scanned with a plurality of primary electron beams in the embodiment of FIG. 48A. FIG. 49A is a more detailed illustration of the embodiment of FIG. 48A. FIG. 49B is a diagram for explaining a primary electron beam irradiation method according to the embodiment. FIG. 50 is a flowchart showing an embodiment of a semiconductor device manufacturing method according to the present invention. FIG. 51A is a flowchart showing a lithography process that is the core of the wafer processing process of FIG. FIG. 51B is a flowchart showing a lithography process that is the core of the wafer processing process of FIG. FIG. 52 is a schematic configuration of an example of a projection type electron beam inspection apparatus. FIG. 53 is a diagram showing the movement of secondary electrons emitted from the rectangular area. FIG. 54 is a diagram showing an electric field distribution of a conventional E × B separator. FIG. 55 is a view showing a vacuum chamber and an XY stage of a conventional charged beam apparatus, [A] is a front view and [B] is a side view. 56 is a diagram showing the relationship between the hydrostatic bearing used in the XY stage of FIG. 1 and the differential exhaust mechanism.

Claims (1)

In an imaging apparatus that irradiates a target with an electron beam emitted from an electron gun, detects electrons emitted from the target using a detector, collects image information of the target, inspects defects of the target, etc.
Charge control means for equalizing or reducing the charge charged to the object, the charge control means, an electrode disposed close to the object, a changeover switch electrically connected to the electrode, A voltage generator electrically connected to one terminal of the changeover switch; a charge detector electrically connected to the other terminal of the changeover switch; the detector; a changeover switch of charge control means; a voltage; A generator and a timing generator for instructing operation timing to the charge detector, and the detector is arranged in the vicinity of the target by using the idle time after the image has been captured for one scan. The charge amount of the electrode is measured, a voltage for irradiating electrons corresponding to the measured charge amount is generated by the voltage generator, and after the measurement, the changeover switch is operated to connect the electrode to the voltage generator. An imaging device, and a voltage generated by the voltage generator to offset the charged electric by applying to said electrode, characterized in that it is configured to perform each scanning operation for the offset.

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