WO2002075806A1

WO2002075806A1 - Method for inspecting wafer, focused ion beam apparatus and transmission electron beam apparatus

Info

Publication number: WO2002075806A1
Application number: PCT/JP2001/002131
Authority: WO
Inventors: Fumio Mizuno; Tsuyoshi Ohnishi
Original assignee: Hitachi, Ltd.
Priority date: 2001-03-16
Filing date: 2001-03-16
Publication date: 2002-09-26
Also published as: JPWO2002075806A1

Abstract

A method and an apparatus for inline inspecting the thickness of a film deposited on a wafer under fabrication, pattern size, pattern registration accuracy and electrical connection state of a hole during the fabrication of a semiconductor device, an image sensor, or a display device. 'Sample observation by TEM/STEM'is combined with 'sample preparation by FIB apparatus'. The FIB apparatus selects a plurality of designated portions on a wafer as objects according to a sample preparation recipe (37) registered previously, positions a sample cut part automatically, cuts a sample automatically and mounts it automatically on a sample holder for observation used in a TEM or STEM, and prepares a recipe (88) for observing the sample by means of a TEM or STEM. The TEM or STEM automatically aligns the observation area of a plurality of samples mounted on the sample holder for observation according to the observation recipe prepared by the FIM apparatus and inputted to the TEM or STEM and acquires observation data by capturing predetermined sample image.

Description

Description Inspection method for wafer, focused ion beam device and transmitted electron beam device

Technical field

INDUSTRIAL APPLICABILITY The present invention relates to an in-line inspection for inspecting the thickness of a deposited film, a pattern dimension, a pattern overlay accuracy, a hole conduction state, and the like of a wafer being manufactured in the manufacture of a semiconductor device, an imaging device, and a display device. A method and an apparatus therefor. Background art

In the manufacture of semiconductor devices, imaging devices, display devices, etc., it is indispensable to increase the density of transistors and the like in order to achieve high performance and high performance of devices. For example, the density of semiconductor devices has been increasing at a rate of approximately 2.5 times Z three years, and the transistor density of AS ICs listed in the Semiconductor Technology Portfolio is 1999 of 20M T from r · Roh cm ^2, in 2002 54MT r. / cm ^2, 2005 years in the 1 33 MT r. / cm \ and in 201 one year 81 1 MT r. become Roh cm ² and the prediction It has been. In order to achieve such a high density, it is essential to improve the structure of the MOS transistor in addition to miniaturization of the pattern. The structure of MOS transistors is expected to shift from current planar transistors to vertical transistors. As shown in FIG. 17, the vertical transistor has a structure in which source, gate and drain are arranged in a vertical direction. Such a ba

—From the perspective of in-line inspection of changes to physical transistors, from the standpoint of in-line inspection, the measurement of gate length, that is, the measurement of the most important parameter that determines transistor performance, is changed to measurement of film thickness instead of measurement of pattern dimensions. .

In order to measure the gate length of a particle transistor, that is, the gate electrode film thickness in-line, it is necessary to provide a sampling inspection of a wafer in process at a reasonable throughput. Small area in the local area with a measurement variation of less than nm. High-precision measurement is an issue. At present, in-line film thickness inspection of deposited films and thermal oxide films generally uses an optical interference-type film thickness measurement device using a light beam and an ellipsometer for a pilot wafer dedicated to inspection. . However, it is a well-known fact that in the very near future, these technologies will not be able to meet increasingly stringent precision requirements. Future candidates for more accurate film thickness measurement methods include: (1) an ellipsometer that uses UV light as the irradiation light, (2) a method of irradiating X-rays to the measurement location and measuring reflected X-rays, etc. ) A method of irradiating a measurement location with a laser beam to measure elastic waves, etc., and (4) A technique of irradiating a measurement location with a medium-speed ion beam to measure scattered ions and the like. However, it is extremely difficult for any of the methods to measure the film thickness in a local region of about several hundred nm. For example, the gate length measurement accuracy required for a vertical transistor with a gate length of 50 nm (including all measurement variations such as sample-induced variations and instrument differences between measuring instruments) is less than 1 nm, which is required. The only methods with spatial resolution that can achieve film thickness measurement accuracy are atomic force microscope (AFM) and transmission electron microscope (TEM) or scanning transmission electron microscope (STEM) that form transmission electron images. is there. At present, only TEM or STEM has the potential because AFM has extremely low throughput. Nevertheless, even in the case of TEM or STEM, the prerequisite for in-line inspection is that it is not possible to perform sampling inspection of wafers in process at a reasonable throughput.

In view of such circumstances, an object of the present invention is to provide in-line inspection means using TEM or STEM for enabling highly accurate film thickness measurement in a local region of about several hundred nm. Disclosure of the invention

The use of TEM or STEM is the only solution that can achieve high-accuracy film thickness measurement in an extremely small area. However, increasing throughput is the biggest challenge. In order to achieve high throughput, it is essential that (1) samples can be prepared at high speed and (2) samples can be observed in a short time. As for (1), the focused ion beam system (F IB device) is the best choice. In this case, the actual time required for the inline inspection is determined by the time required to prepare the sample in the FIB apparatus. In order to enable high-speed sample preparation and sample observation in a short period of time, the FIB device cuts out samples from multiple specified locations on the wafer according to a pre-registered sample preparation recipe. The position is automatically positioned, the sample is automatically cut out, and the cut sample is automatically mounted on an observation sample holder used for TEM or STEM, and a recipe for observing the sample with TEM or STEM is created. In TEM or STEM, in order to enable sample observation in a short time, multiple samples mounted on the observation sample holder are prepared according to the observation recipe input to the TEM or STEM by the FIB device. Automatically align the observation area and acquire a predetermined sample image. On the other hand, in order to make the film thickness measurement with TEM or STEM more accurate, the parallelism between the electron beam incident direction and the observation film surface can be confirmed and corrected. A cross-sectional observation sample composed of a plurality of pattern groups whose observation patterns are slightly shifted in the direction perpendicular to the processing cross section is used so that an observation cross section accurately formed at a predetermined position can be obtained.

According to the present invention, 'sample observation by TEM / S TEM' is combined with 'sample preparation by FIB device', and FIB device targets a plurality of specified locations on a wafer according to a pre-registered sample preparation recipe. A recipe for automatically positioning the sample extraction location, automatically extracting the sample, automatically mounting the extracted sample in an observation sample holder used for TEM or STEM, and observing the sample with TEM or STEM. On the other hand, in the TEM or STEM, the observation area is automatically set for multiple samples mounted on the observation sample holder according to the observation recipe created by the FIB device and input to the TEM or STEM. High-precision in-line film thickness measurement for a local region of several hundred nm by acquiring a predetermined sample image and obtaining observation data. It becomes possible.

In addition, the use of TEM or STEM makes it easy to perform composition analysis, structural analysis, and electronic state analysis of ultra-small regions in addition to high-resolution sample image formation. Conventionally, it was considered difficult because these analysis and analysis information can be used in combination. ) Measurement of film thickness of each layer of laminated film, measurement of three-dimensional shape of pattern, measurement of pattern overlay accuracy, measurement of conduction state of wiring connection part, measurement of particle size of film forming substance, composition distribution of trace impurities in film and Defect measurement compared to a predetermined reference image can be performed accurately and precisely.

By integrating these in-line measurement data, more advanced process management and transistor characteristic analysis can be realized. For example, by in-line measurement of the gate insulation thickness and the dopant concentration profile of the source / drain regions simultaneously with the gate length, it is possible to accurately predict the electrical characteristics of the transistor, such as the threshold voltage, in real time. Becomes That is, data for precisely managing device performance and reliability and yield, which has never been possible in the past, can be obtained by in-line inspection.

In addition, since inspected samples can be stored, they can be removed from storage and re-examined in the event of a yield or reliability problem at a later date. This simplifies failure analysis, which is difficult without physical components.

The wafer inspection method, focused ion beam device, and transmitted electron beam device according to the present invention are as follows.

(1) In a method of inspecting a wafer in a semiconductor device manufacturing process, a step of loading a wafer to be inspected into a focused ion beam device and automatically positioning a sample cutting portion on the wafer according to a sample preparation recipe read in advance. A step of cutting out a predetermined sample from the wafer by using a focused ion beam; a step of mounting the cut out sample on an observation sample holder; and a mounting position of the cut sample on the observation sample holder. Creating an observation recipe in which information relating to the specimen and inspection conditions of the sample are described in association with each other; loading the observation sample holder into a transmission electron beam device; and performing the observation recipe using a transmission electron beam device. And a step of automatically positioning the sample on the observation sample holder according to the read observation recipe. And a step of acquiring predetermined observation data from the positioned sample according to the observation recipe. In the sample preparation process using a focused ion beam apparatus, rapid sample preparation becomes possible by appropriately using a shaped beam, a variable shaped beam, or a cell projection beam as a focused ion beam. A cell projection can be composed of at least a C-shape and a spot. TEM or STEM can be used as the transmission electron beam device. It is preferable that the transmission of the observation recipe between the focused ion beam apparatus that executes the sample preparation step and the transmission electron beam apparatus that executes the sample observation step is performed online via a LAN or the like.

(2) In the wafer inspection method described in (1), the step of creating an observation recipe includes the steps of reading a code written on the observation sample holder, and mounting the code on the observation sample holder using the code as a key. A method for inspecting a wafer, comprising creating a recipe for a transmission electron beam apparatus for observing a sample that has been etched.

When cutting out a sample with the FIB device, the code on the sample, which is the unique number of the sample attached to the sample using the FIB, is used as a key, and the recipe for the transmitted electron beam device for observing the sample is automatically set. Alternatively, it may be created semi-automatically.

(3) In the wafer inspection method according to (1) or (2), in the step of acquiring the observation data, at least one of image data, composition analysis data, structural analysis data, and electronic state analysis data of the sample is obtained. A wafer inspection method characterized by acquiring.

Obtained observation data includes film thickness measurement, pattern shape / dimension measurement, pattern overlay measurement, wiring connection conduction state measurement, particle size measurement, dopant concentration profile measurement, and defects compared to a predetermined reference image. Can be used for measurement. The measured data can be used for process management and device characteristic analysis.

(4) a sample stage that can hold and move a wafer, a stage driving unit that drives the sample stage, a unit that forms a focused ion beam, and that the focused ion beam is placed on a wafer held by the sample stage. In the focused ion beam apparatus including a deflector for scanning, a detector for detecting a sample signal generated from the sample by the focused ion beam irradiation, a sample manipulator for sample handling, and a control unit, The stage driving unit and / or the stage driving unit according to a pre-registered sample preparation recipe. Or a function of controlling the deflector to automatically position a sample cutting portion on a wafer; a function of controlling a predetermined sample using the focused ion beam; and a function of controlling the sample manipulator to cut the sample. The function of mounting the sample on the observation sample holder used in the observation device, the sample mounting position on the observation sample holder, the information described in the sample preparation recipe for the sample, and the information from the memory based on the information A focused ion beam apparatus having a function of creating an observation recipe to be used in the observation apparatus using the read information stored in advance.

The cut sample may be marked with a code for identifying the sample with a focused ion beam. The sample cut from the wafer is once fixed to a sample manipulator, and then moved to one or both of the sample manipulator and the observation sample holder to be mounted on a predetermined address position of the observation sample holder. The sample can be fixed to the sample manipulator using the ion beam assisted film deposition method or the electrostatic adsorption between the manipulator and the sample.

(5) A sample stage that holds and moves an observation sample holder on which a sample is mounted, a stage drive unit that drives the sample stage, and a unit that irradiates the sample by narrowing down the electron beam. A transmission electron beam device including a deflector for deflecting the electron beam, a transmission electron detector for detecting an electron beam transmitted through a sample, and a control unit, wherein the control unit is a focused ion beam device. According to the created observation recipe, a function of performing control for automatically positioning an observation area for a sample on the observation sample holder manufactured by the focused ion beam device, and a function for acquiring predetermined observation data A transmission electron beam device having a function.

Observation data can include sample image data, composition analysis data, structural analysis data, electronic state analysis data, and the like. The transmission electron beam apparatus can include a characteristic X-ray analyzer, an Auger electron spectrometer, and an energy analyzer for characteristic loss electrons. The composition analysis data can be obtained by equipping the transmission electron beam device with, for example, a characteristic X-ray analyzer or an energy spectrometer, and the structural analysis data can be obtained by equipping a transmission electron two-dimensional array detector. The electronic state analysis data can be obtained by providing a transmission electron energy spectrometer. Based on the acquired observation data, film thickness measurement, pattern shape / dimension measurement, pattern overlay measurement, wiring connection conduction state measurement, particle size measurement, dopant concentration profile measurement, and comparison with a predetermined reference image Defect measurement and the like can be performed. The obtained measurement data can be used for process management and device characteristic analysis. Observation data, measurement data, process management data, etc. can be output as electronic data. The process management data to be output can be, for example, a wafer map describing pass / fail of the inspection, or data summarized as an inspection failure rate, the number of inspection failures, and a defect classification result. The transmitted electron beam device preferably has a function of calibrating the observation magnification by a crystal lattice image.

(6) means for loading / unloading the sample holder, storage means for storing a sample observation recipe, sample holder identification means for identifying the sample holder, and control means, wherein the control means Reading an observation recipe corresponding to the sample holder from the storage unit based on the identification result by the sample holder identification unit, and controlling each unit based on the observation recipe to observe the sample. Transmission electron beam device.

The cross-section observation sample prepared by the focused ion beam apparatus can be prepared so that the observation pattern is composed of a plurality of pattern groups that are slightly shifted in a direction perpendicular to the processing cross section. When observing the cross-sectional observation sample, the most appropriate pattern is selected by using the pattern with the largest dimension as the pattern to be inspected. When a cross-section observation sample having at least one step is used for the observation cross-section, the angle of incidence between the cross-section and the observation beam can be obtained from the transmission image. The information on the incident angle of the observation beam can be used to control the tilt angle of the sample or to control the incident beam by a deflector to control the beam incident angle to a predetermined value. Alternatively, the measurement data can be corrected based on the obtained incident angle. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a schematic configuration of an example of a FIB device according to the present invention.

FIG. 2 is a diagram showing a schematic configuration of a TEM or STEM according to the present invention. FIG. 3 is a conceptual diagram of an inline inspection in a semiconductor device manufacturing process according to the present invention.

FIG. 4 is a flowchart illustrating a process for preparing an observation sample holder.

FIG. 5 is a flowchart illustrating a sample preparation process and an observation recipe generation process.

FIG. 6 is an explanatory diagram of a step of cutting out a sample from a wafer using a focused ion beam.

FIG. 7 is a diagram showing an example of a cell projection aperture for obtaining a shaped ion beam.

FIG. 8 is a schematic diagram showing an example of a sample fixed to an observation sample holder.

FIG. 9 is a diagram showing an example of items described in the observation recipe.

FIG. 10 is a diagram for explaining an example of how to cut out a sample using the FIB apparatus.

FIG. 11 is a diagram showing an example of a cross-sectional sample with a step.

FIG. 12 is a diagram showing an example of a transmission image of a stepped cross-sectional sample.

FIG. 13 is a flowchart showing a process flow in TEM or STEM according to the present invention.

FIG. 14 is a diagram for explaining an application example of the inspection in the present invention.

FIG. 15 is a diagram illustrating an output example of the inspection result.

FIG. 16 is a diagram showing an example of the arrangement of the sample storage.

FIG. 17 is a diagram schematically illustrating the structure of a vertical MOS transistor. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a schematic configuration of an example of the FIB device according to the present invention. The FIB device is totally controlled by a control unit 31. After being accelerated to a predetermined energy, the ion beam 12 extracted from the ion gun 11 is focused by the converging lens 13 and the objective lens 14, and is focused on the XY stage 22 in the sample chamber 21. Irradiation is performed on the mounted wafer 23 surface. The XY stage 22 is controlled by the stage drive unit 32 under the control of the control unit 31. Driven. The ion beam 12 irradiated on the wafer 23 is deflected by the deflector 15 and scanned on the wafer 23. A stop 16 for cell projection is provided below the converging lens 13. On the other hand, secondary electrons 24 are emitted from the wafer portion irradiated by the ion beam 12. The secondary electrons 24 are detected by a secondary electron detector 25, subjected to signal processing such as amplification and A / D conversion in a signal amplification / processing section 33, and then stored in a memory 34. The image signal stored in the memory 34 is supplied to a display 35 scanning in synchronization with ion beam scanning, and a sample image is displayed on the display 35. This sample image is called a SIM image.

In the sample chamber 21, a wafer held in the wafer carrier 41 is loaded into or unloaded from the XY stage 22. An observation sample holder opening-donor unloading section 43 for loading / unloading a holder for holding an observation sample, a sample manipulator driving section 44, and a reactive gas introducing section 45 are provided. The sample chamber is also provided with an optical microscope 26.

The control unit 31 sets a sample cutting-out position for TEM or STEM observation based on the obtained sample image according to the read sample preparation recipe 37, and monitors the ion beam while monitoring the sample image. Perform processing. The processed sample is cut out from the wafer and used for observation by TEM or STEM. The control section 31 controls each section to control the cutout of the observation sample, and creates an observation recipe 88 described later. The created observation recipe 88 is temporarily stored in the memory 34 and output to the TEM or STEM for sample observation and the database via the LAN. The observation recipe will be described later.

FIG. 2 shows a schematic configuration of a TEM or STEM according to the present invention. The device is generally controlled by a control unit 81. The electron beam 62 emitted from the electron gun 61 is accelerated to a predetermined energy, then narrowed down by the converging lens 63, and the sample surface on the sample holder 66 mounted on the XY stage 65 Is irradiated. The XY stage 65 is driven by the stage drive unit 82 under the control of the control unit 81. The transmitted electrons 71 transmitted through the sample are detected by the transmitted electron detector 73 through the objective lens 72, and the signal T / JP01 / 02131 Amplification. Amplification and signal processing such as A / D conversion in the processing unit 83 are stored in the memory 84. The image signal stored in the memory 84 is supplied to a display 85 that is being scanned in synchronization with electron beam scanning, and a sample image is displayed on the display 85. The sample holder 66 holding the sample is loaded or unloaded on the XY stage 65 by the sample holder loading / unloading unit 86 under the control of the control unit 81.

If a spatial distribution signal of the transmitted electrons 71 is obtained by irradiating the electron beam 62 at one point, a transmitted electron image can be obtained. On the other hand, if the irradiation electron beam is scanned by the deflector 64 and a time-change signal of the transmitted electrons 71 is obtained, a scanned transmitted electron image can be obtained. As a detector, in addition to the transmitted electron detector 73, an X-ray detector 75 that detects characteristic X-rays 74 generated from a sample by electron beam irradiation, or an energy spectrometer 76 that performs energy spectroscopy of transmitted electrons 71, etc. Is provided. The observation of the sample is performed in accordance with the observation recipe 88 created by the FIB device and transmitted, for example, via the LAN.

FIG. 3 is a diagram showing the concept of in-line inspection in a semiconductor device manufacturing process according to the present invention. An in-line inspection process is provided in the middle of the wafer process and the semiconductor process processes 91 and 92 before and after the illustrated process. The in-line inspection process is roughly divided into two processes: a sample preparation process in a FIB device and a sample inspection process in a TEM / S TEM.

In the sample preparation process of the FIB device, according to the pre-registered sample preparation recipe 37, a plurality of specified locations on the wafer were targeted, the sample extraction locations were automatically positioned, and the sample was automatically extracted and extracted. The sample is automatically mounted on the sample holder for observation used in TEMZSTEM, and an observation recipe 88 for observing the sample by TEM / STEM is created.

In the sample inspection process of the TEMZS TEM, the observation area is automatically aligned for multiple samples mounted on the observation sample holder in accordance with the observation recipe 88 prepared by the FIB device and input to the TE MZS TEM. Then, by acquiring a predetermined sample image, the inspection is performed on a local region of about several hundred nm. Each is described below.

First, referring to FIGS. 4 and 5, the sample preparation process in the FIB apparatus will be described. I will tell. In this step, a sample is cut out, an observation sample is prepared, and an observation recipe 88 is prepared by TEM / STEM.

FIG. 4 is a flowchart illustrating a process for preparing an observation sample holder for loading a sample cut by the FIB apparatus. First, in step 11, a sample holder carrier containing an empty observation sample holder is mounted on the observation sample holder load / unload section 43 of the FIB device. Next, in Step 12, the observation sample holder is taken out of the sample holder carrier, and after confirming that it is empty by the detector attached to the mouth-to-door port 43, Step 1 Proceed to 3, and the holder number written on the holder is read by the holder number reader attached to the load / unload section. Thereafter, the observation sample holder is transported and loaded at a predetermined position in the sample chamber 21 of the FIB device in step 14. The holder number of the observation sample holder is a code unique to each observation sample holder, and is used to identify each observation sample holder. The main body of the sample holder for observation can be reused repeatedly.

The process for preparing the observation sample holder shown in Fig. 4 must be completed before step 30 using the idle time of sample preparation and observation recipe creation process shown in Fig. 5. I just need.

FIG. 5 is a flowchart showing the flow of the sample preparation processing and the observation recipe preparation processing. In step 21, the wafer carrier 41 containing the wafer to be inspected is mounted on the wafer unloading unit 42. In step 22, the wafer to be inspected is taken out of the wafer carrier, and in step 23, it is conveyed to the bri-alignment unit and pre-aligned. The pre-alignment is an operation for detecting an orientation flat or a notch of the wafer, and adjusting the mounting direction of the wafer to the direction of the XY stage 22 of the FIB apparatus based on the detected orientation flat or notch.

After the wafers are aligned, in step 24, the wafer number formed on the wafer is read by a wafer number reader (not shown) incorporated in the FIB apparatus. The wafer number is a unique code for each wafer, and is used to identify the individual wafer or the name of the wafer or the name of the in-process process. In Step 25, Using the read wafer number as a key, a sample preparation recipe 37 corresponding to this wafer registered in advance is read. The sample preparation recipe 37 defines a sample extraction procedure, extraction conditions, and extraction result output conditions from a wafer, and is generally set for each type of product to which the wafer belongs and the name of the in-process process. Subsequent operations are performed automatically or semi-automatically according to this recipe 37.

After reading the recipe, in step 26, the wafer is transferred to and loaded on the XY stage 22 in the sample chamber 21. In step 27, the wafer 23 loaded on the XY stage 22 is used by using the optical microscope 26 mounted on the upper surface of the sample chamber 21 and the alignment pattern formed on the wafer 23. , Will be aligned. The alignment is an operation for aligning the coordinate system of the wafer 23 with the coordinate system of the Y stage 22.The optical microscope image of the alignment pattern is compared with a previously registered alignment pattern reference image. The stage position coordinates are corrected so that the field of view is exactly overlapped with the field of view of the reference image. In step 28, the wafer 23 after the alignment is moved to the stage at a predetermined sample cutout position, and the cutout position is positioned using the SIM image.

After positioning the cutout, proceed to step 29 and irradiate a focused ion beam whose beam shape is shaped to be suitable for high-speed processing to a predetermined size (for example, a few hundred square meters and a thickness of several hundred nanometers). Is cut out, and the cut sample is fixed to a sample manipulator. FIG. 6 is a view for explaining a step of cutting out and retrieving a sample from the wafer 23 using a focused ion beam. In cutting out the sample, for example, a diaphragm 16 for cell projection as shown in FIG. 7 is used in order to achieve both high-speed machining and finishing with high positioning accuracy. The aperture 16 for cell projection includes a C-shaped cell portion 101 having a C-shaped beam transmitting portion 102 and a spot beam portion 105. In the C-shaped cell portion 101, the central portion 103 is a cut-out sample portion, and the beam-shaped portion 104 connecting the central portion 103 to a peripheral portion is a sample support portion during processing.

As shown in Fig. 6 (a), the C-shaped cell portion 101 on the left side of the beam stop 16 is irradiated with a focused ion beam to form a C-shaped beam. Switch the beam irradiation position to the spot beam section 105 on the right side to form a narrow spot beam Then, finish processing is performed as shown in Fig. 6 (b). In the processed part of the wafer, an observation sample part 106 is formed corresponding to the central part 103 of the C-shaped cell part 101 of the beam stop 16, and corresponding to the beam part 104. A support 107 is formed. At the time of cutting, a reactive gas for assisting ion etching is introduced from the reactive gas introduction part 45 in order to obtain a high processing speed and a smooth processing section, and the vicinity of the ion beam irradiation point is changed to a reactive gas atmosphere. I do. For example, a fluorine-based gas is introduced into the vicinity of the processing location for processing a silicon oxide film and a chlorine-based gas for processing metal wiring. A section or a plane is selected as the section according to the observation purpose.

As shown in FIG. 6 (c), the sample is fixed to the sample manipulator 108 after cutting the lower portion of the sample piece by tilting the wafer. The sample is fixed to the sample manipulator 108 by, for example, bringing the tip of the manipulator into contact with the top surface of the sample in an atmosphere of a tungsten compound gas and irradiating the contact portion with an ion beam to form the tungsten film 109. To achieve. The sample is supported by the tungsten film 109 and fixed to the sample manipulator 108 as shown in FIG. 6 (d). After that, as shown in FIG. 6 (e), the support portion 107 is cut by the focused ion beam to cut out the sample 110. The sample was fixed to the manipulator by bringing the tip of the manipulator into contact with the sample surface, controlling the manipulator drive unit 44, applying a voltage to the manipulator, and utilizing the electrostatic action between the sample and the sample. By generating an attractive force, the manipulator may be electrostatically attracted and fixed.

Returning to FIG. 5, in step 30, the sample 110 fixed to the sample manipulator 108 is loaded into a predetermined position in the sample chamber 21 by moving the sample manipulator and / or the sample holder for observation. The sample is transferred onto the observation sample holder. FIG. 8 is a schematic diagram showing an example of a sample fixed to the observation sample holder 66. Fig. 8 (a) is a top view of the observation sample holder loaded with the sample, and Fig. 8 (b) is a cross-sectional view along AA '. The sample holder for observation 66 shown in the figure has a carbon thin film 123 supported on one end of a cylindrical main body 121 by a metal mesh 122, and is provided in each section defined by the metal mesh 122. An address has been assigned. The cut-out samples 13 1 to 13 4 are specified in the sample preparation recipe 37 on the observation sample holder or based on the sample preparation recipe. Is loaded into a pre-registered address position read from the memory. On the other hand, in step 31, the control unit 31 of the FIB apparatus stores information such as the name of the sample, the name of the in-process process, the address number of the die to which the sample belongs, the address position on the observation sample holder, and the inspection contents. Is used to create an observation recipe 88 with the same holder number. Observation recipe 8 8 defines the observation procedure, observation conditions, and observation result output conditions for the sample mounted on the observation sample holder. Prior to the preparation of the observation recipe 88 in step 31, the TEM / STEM recipe for the holder number of the observation sample holder carried into the sample chamber 21 of the FIB device has already been stored in the memory 34 of the FIB device. If it exists, it is a recipe for a previously observed sample, so delete the receiver and initialize the contents of the observation recipe.

In step 32, for the wafer on the XY stage, it is determined whether sample cutting and removal at all locations specified in the sample preparation recipe 37 and mounting on the observation sample holder have been completed. Repeat steps 28 to 31 until all samples have been cut out.

In step 33, the observation sample holder for which the mounting of the sample has been completed and the wafer for which the sample has been cut out are returned to the respective carriers. On the other hand, since the observation recipe 88 created in step 31 is input to the TE MZ STEM used for inspection, it is output in step 34 via a communication line or using a storage medium. You. If unprocessed wafers to be inspected remain in the wafer carrier as determined in the next step 35, the processing from step 21 is repeated for those wafers.

Figure 9 shows an example of the items described in the observation recipe 88. In the exemplified observation recipe 88, information such as a product holder number, a lot name, a wafer number, a die address, and the like are described as information relating to the sample holder, and information relating to the wafer from which the sample has been cut out, as information relating to the sample holder. In addition, information such as specimen address in the holder, inspection item, inspection procedure, acceleration voltage, beam current, detection signal, and detection result output are described as the inspection information. In the example shown in the figure, for example, the sample mounted on the sample address A-1 in the holder has a polysilicon film thickness of 100 kV by STEM and a beam current of 1 nA by the type 3 inspection procedure. Inspection results should be output as a type 2 wafer map It has been instructed. In FIG. 9, types such as an inspection procedure and an inspection output mean that data whose data is registered in advance is used.

Of these pieces of information, the sample holder number was obtained in step 14 in Fig. 4.Information such as the product name, lot name, wafer number, and die address related to the wafer from which the sample was cut was used as the sample preparation recipe. It is the information described in 37. Among the inspection information, the information such as the sample address in the holder, inspection items, inspection procedure, acceleration voltage, beam current, detection signal, and detection result output are the information described in the sample preparation recipe 37 or the same. Is information registered in advance and read from the memory. In this way, the control unit 31 of the FIB apparatus cuts out the sample from the specified location of the wafer specified according to the sample preparation recipe, loads the sample into the observation sample holder, and specifies the sample on the TEM / STEM side. The information necessary for the observation, that is, the information on the sample holder for observation loaded with the sample and the address information on the holder, and the information on the inspection method of the sample inherited from the recipe for sample preparation are combined to create an observation recipe, Output to TEM / STEM and database via LAN.

FIGS. 10 and 11 are diagrams illustrating an example of how to cut out a sample in the FIB apparatus. For a sample cut from a wafer, it is necessary to make a cross section at the center of the pattern in order to perform high-precision measurements on hole patterns and the like. Even if the irradiation position accuracy of the focused ion beam is somewhat poor, as shown in Fig. 10, the observation pattern is oriented in a direction perpendicular to the processing cross section, so that a cross section is formed near the center of either pattern. It is preferable to use a cross-sectional observation sample composed of a plurality of pattern groups that are slightly shifted from each other. FIG. 10 (a) is a top view of a wafer including a sample cut-out portion 140, and FIG. 10 (b) is a cross-sectional view. In this sample, the test pattern 144 with the maximum lateral length appearing in the cross section is judged to be the optimum test pattern in which the cross section is made at almost the center.

In order to measure the film thickness with TEM / STEM with higher accuracy, it is necessary to make the incident direction of the electron beam parallel to the observation film surface. In order to confirm or correct the parallelism between the electron beam incident direction and the observation film surface, as shown in Fig. 11, a step 15 2 was added to the observation cross section 15 1 of the sample 150. It is good to form. 131 When observing the sample 150 shown in Fig. 11 by TEM / STEM, if the incident direction of the electron beam of TEMZSTEM is not parallel to the observation film surface of the film 153 for measuring the thickness, As shown in b), a transmission image in which the film is discontinuous at the step 152 and the non-step is obtained. In this case, the film thickness T2 measured on the sample image includes an error. On the other hand, when the incident direction of the electron beam of the TEMZ STEM is parallel to the observation film surface, as shown in FIG. A continuous transmission image is obtained at the stepped portion. The measured value T1 in this case accurately represents the thickness of the film 153. Therefore, by tilting the XY stage of the TEMZS TEM or adjusting the incident direction of the electron beam 62, the film thickness measurement is performed so that a TEM image or STEM image as shown in FIG. 12 (a) is formed. If this is done, it is guaranteed that the incident direction of the electron beam is parallel to the observation film surface, so that accurate film thickness measurement values can be obtained.

Next, the inspection method using TEM or STEM and the output method of the inspection result will be described. FIG. 13 is a flowchart showing the flow of processing in TEM or STEM.

In step 41, the sample holder carrier on which the observation sample holder to be inspected is placed is transported from the FIB device to the TEM STEM by an automatic carrier or by an operator, and is mounted on the mouth-to-door portion 86 of the sample holder carrier. In step 42, the holder number written on the observation sample holder is read by the holder number reader attached to the load / unload section 86. At step 43, the observation recipe 88 corresponding to the observation sample holder, which has been read by the FIB apparatus and transferred to the TEM / STEM and overwritten, is read out using the read folder number as a key. Subsequent operations are performed automatically or semi-automatically according to the observation recipe 88. In step 44, after taking out the observation sample holder to be measured from the holder carrier, the observation sample holder is loaded in a predetermined direction on the XY stage 65 in the sample chamber held in a vacuum. In the following step 45, the observation sample holder 66 loaded on the XY stage 65 is stage-moved to the address where the first sample specified by the observation recipe 88 is located, and the observation point is positioned. When positioning the observation point, the observation pattern should be

In the case of a pattern group, for example, by selecting the cross section of the test pattern with the largest horizontal line length, the test pattern with the cross section formed near the center of the pattern is selected as the observation point. If a step as shown in Fig. 11 is formed in the processed cross section of the sample, adjust the incident direction of the electron beam 62 or the tilt of the XY stage 65 to adjust the inclination as shown in Fig. 12 (a). By making the lines on the film upper surface and film lower surface formed by the non-step portion and the step portion to be observed as straight lines, the electron beam and the observation film surface can be made parallel. Instead of adjusting the incident direction of the electron beam 62 or the tilt of the XY stage 65, the angle between the electron beam 62 and the surface of the observation film is obtained, and the obtained angle is used to measure the film thickness. May be corrected.

Next, proceed to step 46, irradiate the sample with an electron beam 62 according to the instructions of the observation recipe 88, elemental analysis using transmission electron image formation and characteristic X-ray analysis, and electron energy monochromator. Perform energy analysis of transmitted electrons using 7.6. The transmission electron image may be a projection image obtained by a normal transmission electron microscope or a scanning image obtained by a scanning transmission electron microscope. Scanned images are easier to interpret and handle than projected images, as there is no change in diffraction contrast due to slight differences in focal position.

Then, the obtained transmission electron image and Z or elemental analysis information are analyzed to determine the thickness of the thin film at a predetermined portion and the shape and dimension of the pattern as shown in the cross-sectional example of the hole pattern in FIG. 14 (a). Top diameter dl, bottom diameter d2, height h, inclination angle, superposition d3 of pattern 161 and pattern 162 as shown in the cross-section example in Fig. 14 (b), Fig. 14

Conduction and non-conduction of the hole 163 as shown in the cross-sectional example of (c), and grain size of the deposited film as shown in the cross-sectional example of Fig. 14 (d) (164 is the crystal grain, 165 Is the grain boundary), and the dopant concentration profile in the dopant layer 166 as shown in the cross-sectional example of Fig. 14 (e).

16 7 、 Detection of defects 16 8 in comparison with the pre-stored reference image as shown in the cross-section example of the deposited film in Fig. 14 (f) (Detection of difference by comparing the sample image with the reference image) And outputs the difference as a defect 168). The analysis of observation data may be performed in real time, or only transmission images or data of each sample may be acquired and stored, and the analysis may be performed offline. Elemental information obtained from elemental analysis and transmitted electron energy analysis not only determines compositional state, but also determines thin film thickness, pattern geometry, hole conduction / non-conduction, crystal grain size, dopant concentration profile, etc. Indispensable to do. For example, when measuring the thickness of the _{_{S i 0 2 / S i 3}} N 4 multilayer film, contrast difference between them appearing in transmission electron image is small, the boundary of the two membranes only from image analysis of transmission electron image That is, it is difficult to determine the film thickness accurately. However, by detecting and comparing characteristic X-rays, Auger electrons, or characteristic energy-loss electrons, the boundary between the two can be determined more precisely.

The transmission electron image and the element concentration profile are compared with the reference image of the inspection location stored in advance, and defects detected as the differences between the transmission electron image and the element concentration profile are abnormal in the film thickness, shape and dimensions, as well as in the hole filling portion and These include plug pinholes, poor coverage of deposited films, and crystal defects such as stacking faults. The detected defects are classified according to a predetermined automatic defect classification algorithm.

Returning to FIG. 13, the inspection of all the samples on the observation sample holder is performed by repeating the processing from Step 45 to Step 46. If it is determined in step 47 that the inspection of all the samples on the sample holder has been completed, the process proceeds to step 48 to unload the observation sample holder into the sample holder carrier. Then, the process proceeds to step 49, where an inspection result is created and output based on the measurement data obtained in step 46. If it is determined in step 50 that there is an untested observation sample holder in the sample holder carrier, the processing of steps 42 to 49 is repeated for that.

The output form of the inspection result in step 49 may be the sample image or the observation data as it is, but in general, a wafer map describing the pass or fail of the inspection as shown in Fig. 15 or an inspection failure rate It is output in the form of the number of inspection failures or defect classification results. By clicking on the inspection die on the wafer map, the sample image and raw observation data corresponding to the die can be displayed together. Not only charts such as wafer maps and charts but also processed reports can be output. In addition, output to a higher-level inspection data management system via a communication line or storage medium Although it is common, it can also be output as printed matter.

Furthermore, by integrating these in-line measurement data, data for more advanced process management and transistor characteristic analysis can be obtained. For example, in-line measurement of gate insulating film thickness and dopant concentration profile of source / drain regions at the same time as gate length can provide data for real-time accurate prediction of transistor electrical characteristics such as threshold voltage. . These data are output to a higher-level production management system, and are used to precisely control device performance reliability and yield.

After the inspection, the sample holder carrier is sent to the sample storage connected to the TEM or STEM by a transporter, and the inspected sample is stored in the sample storage while being placed on the observation sample holder. These samples are kept in stock using the wafer number, product name, process in process, and holder number as keys, and can be removed at a later date if a yield or reliability problem occurs. Will be reviewed again. In addition, considering the consistency of the processing time between the FIB device and the TEMZS TEM, the sample storage may be placed between the FIB device and the TEM / STEM as a buffer, as shown in Fig. 16. Good.

The calibration of TEM or STEM magnification is performed by observing a crystal lattice image. This results in very accurate dimensional and shape measurement data. The inside of both the wafer carrier and the sample holder carrier is kept in a clean atmosphere. In particular, when analyzing the composition of a sample, the sample holder carrier used is designed so that the sample is not contaminated.

In this example, the SIM image was used to position the cutout. However, a high-resolution optical microscope or scanning electron microscope (SEM) was built in the focused ion beam device, and the optical microscope image or SEM image was used. It is also possible to perform positioning using. Positioning using an optical microscope image or SEM image instead of the SIM image can further reduce damage to the wafer due to the positioning.

Further, in this embodiment, the observation sample holder is numbered, and the inspection by TEM / STEM is controlled using the holder number. At the same time, the sample number is stamped on each sample with the focused ion beam, and the sample number is The observation recipe 88 may be created by using, and the inspection work may be controlled. In this embodiment, a force is shown in which a plurality of samples cut out from one wafer are placed on one observation sample holder. ^ A plurality of samples cut out from one wafer are used for a plurality of observations. The sample may be placed over the sample holder, or samples cut out from a plurality of wafers may be collectively placed on one observation sample holder. Regarding the inspection content, it is also possible to perform multiple types of inspections on one sample, or to change the inspection content individually for the samples in the observation sample holder.

In the present embodiment, the case where the specification of the sample cutout location in the FIB apparatus is determined in advance for each product name, in-process process name, but the specification of the sample cutout location in the recipe is determined by the defect position coordinate data of the defect inspection apparatus or the like. It is also possible to overwrite differently for each wafer, such as specifying the position coordinates on the wafer map of the operator. In addition to determining the cutout location for each product name and in-process process name, if defect position coordinate data can be overwritten for each wafer, it can be used for review inspection after defect inspection etc. become.

In the present embodiment, a tungsten support film was used for fixing the sample to the sample manipulator, but the deposition film for fixing is not limited to this.

In the present embodiment, the case where the FIB device and the TEMZ STEM are both configured as a stand-alone device has been described. However, the FIB device and the TEMZSTEM can be configured as one device including the FIB device and the TEMZS TEM. It is also possible to connect multiple TEMZSTEMs to one FIB device.

Confirmation and correction of the cross-section observation sample composed of multiple pattern groups in which the observation pattern is slightly shifted in the direction perpendicular to the processing cross section, and the parallelism between the incident direction of the observation beam and the observation film surface In order to be able to do this, the cross-section samples processed with steps can be used not only for TEM / STEM but also for various observation devices such as SEM and optical microscope.

In this embodiment, the manufacture of a semiconductor device is described as an example, but the present invention can be applied to the manufacture of similar devices such as an image sensor and a display device. Industrial applicability 'Τ EM or ST EM sample observation, combined with' FIB device sample preparation, '(1) FIB device targets specified multiple locations on wafer according to pre-registered sample preparation recipe Automatically position the sample extraction point, automatically extract the sample, automatically mount the extracted sample on the observation sample holder used in TEM / STEM, and observe the sample using TEM / STEM. (2) TEMZSTEM targets multiple samples mounted on the observation sample holder according to the observation recipe created by the FIB device and input to the TEM / S TEM. By automatically aligning and acquiring a predetermined sample image, it is possible to perform highly accurate in-line film thickness measurement on a local region of about several hundred nm.

Using TEM / STEM, it is possible to perform composition analysis, structural analysis, and electronic state analysis of ultra-small regions in addition to high-resolution sample image formation. The combination of these analysis and analysis information makes it possible to measure the thickness of each layer in the in-line film, measure the three-dimensional shape of the pattern, measure the pattern overlay accuracy, and measure the wiring connection, which has been considered difficult in the past. This makes it possible to accurately and precisely measure the conduction state of the film, measure the particle size of the film-forming substance, measure the composition distribution of trace impurities in the film, and measure the defects in comparison with a predetermined reference image. By integrating these inline measurement data, more advanced process management and transistor characteristic analysis can be realized. For example, in-line measurement of gate insulating film thickness and dopant concentration profile of source / drain regions, as well as gate length, enables accurate prediction of transistor electrical characteristics such as threshold voltage in real time. In other words, data that can accurately manage the performance reliability and yield of devices, which has never been possible before, can be acquired by in-line inspection.

In addition, the ability to observe the crystal lattice image makes it extremely easy to calibrate the magnification of the device. And accurate measurement data of very accurate dimensions and shapes can be obtained.

Claims

The scope of the claims

1. In a wafer inspection method in a semiconductor device manufacturing process,

Loading the focused wafer into the focused ion beam device;

Automatically positioning a sample cutting location on the wafer according to a sample preparation recipe read in advance;

Cutting a predetermined sample from the wafer by a focused ion beam, mounting the cut sample on an observation sample holder,

Creating an observation recipe in which information relating to the mounting position of the cut sample on the observation sample holder and information relating to the inspection conditions of the sample are described; and loading the observation sample holder into a transmission electron beam apparatus. The process of

Reading the observation recipe with a transmission electron beam apparatus,

Automatically positioning the sample on the observation sample holder according to the read observation recipe;

Acquiring predetermined observation data from the positioned sample in accordance with the observation recipe.

2. The wafer inspection method according to claim 1, wherein the step of creating the observation recipe includes a step of reading a code written on the observation sample holder, and mounting the code on the observation sample holder using the code as a key. A method for inspecting a wafer, comprising preparing a recipe for a transmission electron beam apparatus for observing a sample that has been etched.

3. The wafer inspection method according to claim 1, wherein the step of acquiring the observation data acquires at least one of image data, composition analysis data, structure analysis data, and electronic state analysis data of the sample. A method of inspecting a wafer, comprising:

4. A sample stage that can hold and move the wafer, a stage driving unit that drives the sample stage, a unit that forms a focused ion beam, and that the focused ion beam is placed on the wafer that is held on the sample stage. A focused ion beam device including: a deflector for scanning with a detector, a detector for detecting a sample signal generated from the sample by the focused ion beam irradiation, a sample manipulator for sample handling, and a controller. A controller configured to control the stage driver and / or the deflector in accordance with a pre-registered sample preparation recipe to automatically position a sample cutting position on a wafer; and a predetermined function using the focused ion beam. A function of controlling the sample to be cut out, a function of controlling the sample manipulator to mount the sample cut out on an observation sample holder used in an observation device, a sample mounting position on the observation sample holder, and the sample. And a function of creating an observation recipe read out from the control unit based on the inspection information and / or recipe described in the sample production recipe and used in the observation apparatus in association with the inspection information of the sample. A focused ion beam device characterized by the above-mentioned.

5. A sample stage that can move while holding an observation sample holder on which a sample is mounted, a stage driving unit that drives the sample stage, a unit that squeezes an electron beam to irradiate the sample, and the electron beam. A transmission electron beam device including a deflector for deflecting the electron beam, a transmission electron detector for detecting an electron beam transmitted through the sample, and a control unit.

A function of performing control for automatically positioning an observation region for a sample on an observation sample holder manufactured by the focused ion beam device, according to an observation recipe created by the focused ion beam device; A transmission electron beam apparatus having a function of acquiring predetermined observation data.

6. Means for unloading the sample holder, storage means for storing a sample observation recipe, sample holder identification means for identifying the sample holder, and control means,

The control unit reads out an observation recipe corresponding to the sample holder from the storage unit based on the identification result by the sample holder identification unit, and controls each unit based on the observation recipe to observe the sample. A transmission electron beam device characterized by the above-mentioned.