JP2000123771A - Scanning electron microscope and defective position analysis method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning electron microscope capable of automatically and correctly taking an image of an objective board without generating artitaets in a provided digital image even in the case of taking the image of any objective board with any magnification, determining the position of a defective part, and analyzing the feature quantity of the defective part and the nature thereof in relation to the defective part, and to provide a defective part analysis method using the scanning electron microscope. SOLUTION: This scanning electron microscope is provided with: a switch control part 108 to control a scanning means 104 by at least switching it so as to provide in a switched fashion, a low-magnification digital image signal based on a wide image-taking visual field and a high-magnification digital image signal based on a narrow image-taking visual field from an A/D converting part 116; and beam spot diameter control parts 203, 106, 110, 105, 109, 101 to control the spot diameter of an electron beam on the surface of an objective board by switching it when the control is performed by switching with the switching control part. This defective part analysis method employs the scanning electron microscope.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention obtains electron beam images having high resolution for various defect sites existing on a target substrate (sample) such as various semiconductor substrates, and obtains the obtained high resolution. The present invention relates to a scanning electron microscope capable of analyzing a characteristic amount or a property of a defect portion based on an electron beam image having the defect image and a defect portion analysis method using the scanning electron microscope.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable progress in miniaturization of circuit patterns formed on target substrates (samples) such as various semiconductor substrates, and the size of defects to be observed is smaller than the wavelength of light. Are also coming out. For this reason, defect observation using an image by a scanning electron microscope has come to be performed instead of optical observation. However, when a defect image is picked up by a scanning electron microscope, there is a problem that even if the target substrate is moved to the position of the defect detected by the appearance inspection device, there is no defect to be observed in the visual field. This is due to the difference in coordinate management between the visual inspection device and the scanning electron microscope, the accuracy error of the individual sample stages of the visual inspection device and the scanning electron microscope, and the magnification at which the image is taken. This is because the magnification of the image is very high compared to the optical magnification of the device and the field of view of the image is narrow.

Therefore, when observing a foreign substance with a scanning electron microscope, it is possible to find the foreign substance most efficiently by selecting a low magnification that allows the search area to be within the field of view at one time. However, when the size of the foreign matter is small, the presence of the foreign matter may not be noticed at a low magnification. Therefore, Japanese Patent Application Laid-Open No. 5-223
Japanese Patent No. 747 (Prior Art 1) discloses a device for observing or analyzing the shape of a foreign substance or a defect by using an optical surface foreign substance inspection apparatus for a wafer or a similar apparatus and wafer coordinates and foreign substance information provided by the apparatus. In a foreign matter observation device provided with an electron microscope that performs, the means for determining the level of the size of foreign matter provided by the optical surface foreign matter inspection device and similar devices, when the foreign matter level is less than a certain value, 2. Description of the Related Art There is known a foreign substance observation apparatus which divides an observation region of the wafer into N × M divided regions, and the electron microscope has a unit for performing divided observation for each divided region.

[0004]

On the other hand, in a microscope such as a scanning electron microscope, the objects to be imaged are various, and the magnification for imaging them is also various values. It is very important to capture an image without generating pseudo noise even under such various conditions. When performing image capturing manually, a person always monitors whether or not pseudo-noise is occurring in an image to be captured. Although it is possible, when observation with the microscope is not performed manually, for example, position information of a plurality of sites on the sample to be observed is input to the microscope in advance, and the plurality of sites are automatically observed to acquire imaging data. In such a case, it is necessary to automatically perform control for preventing the generation of the noise. However, in the above-mentioned prior art 1, sufficient consideration is not given to the point of imaging various substrates (imaging targets) without generating pseudo noise.

[0005] An object of the present invention is to solve the above problems.
Whatever the target substrate is imaged at any magnification, the obtained digital image is automatically and accurately captured without generating pseudo noise, and the position of the defective part is identified and specified. It is an object of the present invention to provide a scanning electron microscope capable of analyzing a feature amount or a property of a defect portion and a defect portion analysis method using the scanning electron microscope.

[0006]

In order to achieve the above object, the present invention provides a scanning electron microscope having an imaging magnification setting section for setting an imaging magnification, and an imaging magnification setting section for setting the imaging magnification. An image is obtained by controlling the spot diameter of the irradiation beam on the sample using information on the magnification and background information on the imaging region. Further, the present invention provides a scanning electron microscope, wherein an imaging magnification setting unit for setting an imaging magnification is provided, and the imaging magnification is set using information on the imaging magnification set in the imaging magnification setting unit and background information on the imaging region. Performing signal processing such as filtering on an analog electric signal converted from the electron beam signal intensity of secondary electrons, reflected electrons, absorbed electrons, and the like from a target substrate (sample) or a digital signal obtained from the analog electric signal. It is characterized by.

Further, the present invention provides a stage on which a target substrate (sample) is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and a converging lens. A scanning unit that two-dimensionally scans the surface of the target substrate with the electron beam converged in, and an objective lens that focuses the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector that detects an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning of the electron beam by the scanning unit and outputs an analog image signal; An A / D converter for sampling an output analog image signal and converting it into a digital image signal, wherein the A / D A switching control unit that switches and controls at least the scanning unit so as to obtain a low-magnification digital image signal based on a wide imaging field of view and a high-magnification digital image signal based on a narrow imaging field from the switching unit. When the switching control is performed by the switching control unit, a beam spot diameter control unit that switches and controls the spot diameter of the electron beam on the surface of the target substrate is provided. The present invention also relates to a scanning electron microscope, which is obtained by switching between a low-magnification digital image signal based on a wide imaging field of view and a high-magnification digital image signal based on a narrow imaging field from an A / D converter. A switching control unit that switches and controls at least the scanning unit, and when switching and controlling by the switching control unit to capture an image in a wide imaging field of view, the electron beam based on information on the surface state at the imaging region of the target substrate. A beam spot diameter control unit for controlling the spot diameter.

Further, the present invention is characterized in that in the scanning electron microscope, the beam spot diameter control section is configured to control the movement of the stage in the direction of electron beam irradiation. Further, the invention is characterized in that, in the scanning electron microscope, the beam spot diameter control unit is configured by controlling the objective lens. Further, according to the present invention, in the scanning electron microscope, the beam spot diameter control unit is configured to control a current of an electron beam emitted from the electron gun. The present invention also relates to a scanning electron microscope, which is obtained by switching between a low-magnification digital image signal based on a wide imaging field of view and a high-magnification digital image signal based on a narrow imaging field from an A / D converter. A switching control unit that switches and controls at least the scanning unit, and suppresses generation of a pseudo noise component from an imaging portion of the target substrate when imaging is performed by switching and controlling by the switching control unit in a wide imaging field of view. And a control unit for controlling.

The present invention also relates to a scanning electron microscope, wherein an A / D converter switches between a low magnification digital image signal based on a wide imaging visual field and a high magnification digital image signal based on a narrow imaging visual field. A switching control unit that switches and controls at least the scanning means so as to obtain an analog image signal that is output from the detector when the switching control unit switches and controls to capture an image in a wide imaging field of view. A signal processing unit that performs signal processing according to the surface state of the imaging portion of the target substrate to reduce high-frequency pseudo noise components.
The present invention also relates to a scanning electron microscope, wherein at least a scanning unit is switched so that a digital image signal based on a wide imaging field of view and a digital image signal based on a narrow imaging field of view can be obtained by switching from an A / D converter. And a switching control unit for controlling the switching by the switching control unit. When imaging is performed in a wide field of view by controlling the switching by the switching control unit, the digital image signal obtained from the A / D conversion unit is subjected to a surface in an imaging region of the target substrate. A signal processing unit that performs signal processing according to the state to reduce high-frequency pseudo noise components. Further, the invention is characterized in that in the scanning electron microscope, the signal processing unit is configured to perform a filtering signal processing.

The present invention is also a scanning electron microscope, which locates a defective portion in a wide imaging field of view based on the position coordinates of the defective portion present on a target substrate mounted on a stage. An electron beam is scanned and radiated onto the located defective portion in a defocused state so as to obtain the wide field of view, an analog image signal is detected from a detector, and the detected analog image signal is converted into an A / A signal. The D conversion unit converts the digital image signal into a low-magnification digital image signal. The position specifying unit specifies the position of the defective portion based on the converted digital image signal indicating the low-magnification defect site. Positioning the defective portion in the narrow imaging field of view based on the position of the defective portion, and obtaining the narrow imaging field of view by focusing the electron beam on the located defective portion. And sea urchin scanning irradiation, detecting the analog image signal from the detector, converts the detected analog image signal to a high magnification digital image signal by the A / D converter,
Analyzing means for analyzing the characteristic amount or the property of the defective portion based on the converted digital image signal indicating the high-magnification defective portion. The present invention also relates to a scanning electron microscope, which locates a defective site within a wide imaging field of view based on the position coordinates of the defective site present on a target substrate mounted on a stage, The electron beam is scanned and irradiated so as to obtain the wide imaging field of view by controlling the generation of the pseudo noise component from the background to the defective portion, and an analog image signal is detected from the detector. The analog image signal
A / D conversion unit converts the digital image signal into a low-magnification digital image signal, and specifies the position of the defective part based on the converted digital image signal indicating the low-magnification defect part. Based on the position of the defective part, the defective part is positioned in a narrow imaging field of view, and the located defective part is scanned and irradiated with an electron beam in a focused state so as to obtain the narrow imaging field of view. An analog image signal is detected from the device, the detected analog image signal is converted into a high-magnification digital image signal by an A / D converter, and based on the converted digital image signal indicating the high-magnification defect portion. Analyzing means for analyzing the characteristic amount or the property of the defect site.

According to another aspect of the present invention, there is provided a scanning electron microscope for positioning a defective portion within a wide field of view based on the position coordinates of the defective portion present on a target substrate mounted on a stage. Scanning and irradiating an electron beam on the located defective portion by controlling a spot diameter based on background information so as to obtain the wide imaging field of view, detecting an analog image signal from a detector, and detecting the detected Position specifying means for converting the analog image signal into a low-magnification digital image signal in an A / D converter, and specifying the position of the defective portion based on the converted digital image signal indicating the low-magnification defective portion; The defective portion is positioned in a narrow imaging field of view based on the position of the defective portion specified by the position specifying means, and the narrow defective imaging is performed with the electron beam focused on the positioned defective portion. Scanning irradiation is performed so as to obtain a field of view, an analog image signal is detected from a detector, and the detected analog image signal is converted into a high-magnification digital image signal by an A / D converter. And analyzing means for analyzing the characteristic amount or the property of the defective portion based on the digital image signal indicating the defective portion. The present invention also relates to a scanning electron microscope, which locates a defective site within a wide imaging field of view based on the position coordinates of the defective site present on a target substrate mounted on a stage, An electron beam is scanned and irradiated on the detected defect portion so as to obtain the wide imaging field of view, an analog image signal is detected from a detector, and the detected analog image signal is set to a background state of the defect portion. The high-frequency pseudo-noise component due to the background is reduced by performing the corresponding signal processing, and the analog image signal in which the high-frequency pseudo-noise component has been reduced is converted into a low-magnification digital image signal by an A / D converter. Position specifying means for specifying the position of the defective part based on the digital image signal indicating the defective part with the low magnification, and the defect based on the position of the defective part specified by the position specifying means. Position within the narrow imaging field of view, and scans and irradiates the located defect site with an electron beam in a focused state so as to obtain a narrow imaging field of view, detects an analog image signal from a detector, and detects the detected position. The A / D converter converts the analog image signal into a high-magnification digital image signal, and analyzes the characteristic amount or the property of the defect portion based on the converted digital image signal indicating the high-magnification defect portion. Means.

According to another aspect of the present invention, there is provided a scanning electron microscope for positioning a defective portion within a wide field of view based on the position coordinates of the defective portion present on a target substrate mounted on a stage. An electron beam is scanned and irradiated on the located defective portion so as to obtain the wide imaging field of view, an analog image signal is detected from a detector, and the detected analog image signal is converted by an A / D converter. The digital image signal is converted into a low-magnification digital image signal, and the converted low-magnification digital image signal is subjected to signal processing in accordance with the background state of the defective portion to reduce high-frequency pseudo-noise components due to the background. Position specifying means for specifying the position of a defective portion based on a digital image signal indicating a low-magnification defective portion with reduced pseudo noise components, and a defective portion specified by the position specifying device The defective portion is located in a narrow imaging field of view based on the position of, and the located defective portion is scanned and irradiated with an electron beam so that a narrow imaging field of view can be obtained in a focused state. Is detected, and the detected analog image signal is converted into a high-magnification digital image signal by an A / D converter, and the characteristic amount of the defective part is determined based on the converted digital image signal indicating the high-magnification defect part. Alternatively, an analysis means for analyzing the property is provided.

Further, according to the present invention, the position specifying means in the scanning electron microscope extracts a difference image signal between a digital image signal indicating a low magnification defect site and a reference digital image signal having no low magnification defect site. Thus, the position of the defective portion is specified. Further, the present invention is characterized in that the position specifying means in the scanning electron microscope includes a display device for displaying a digital image signal indicating a low magnification defect site. Further, according to the present invention, the position specifying means in the scanning electron microscope is configured to acquire a position coordinate of a defective portion existing on a target substrate placed on a stage from a visual inspection device. Features.

Further, the present invention provides a stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and a converging lens for converging the electron beam. Scanning means for two-dimensionally scanning an electron beam on the surface of the target substrate, an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate, and the scanning means A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning of the electron beam by the detector and outputting an analog image signal; and a detector which is detected and output from the detector. An analog image signal which is sampled and converted into a digital image signal by an A / D converter. In the method for analyzing a defective portion, the defective portion is positioned in a wide imaging field of view based on the position coordinates of the defective portion present on the target substrate placed on the stage, and the position of the defective portion is determined. In the defocused state, an electron beam is scanned and irradiated so as to obtain the wide imaging field of view, and an analog image signal is detected from the detector. A digital image signal is converted into a digital image signal, and a position specifying step of specifying the position of the defective part based on the converted digital image signal indicating the defective part with a low magnification is performed. Then, the defective portion is positioned in a narrow imaging field of view, and the electron beam is focused on the located defective portion so that the narrow imaging field of view is obtained by scanning. Then, an analog image signal is detected from the detector, and the detected analog image signal is converted into a high-magnification digital image signal by the A / D converter. And analyzing the characteristic amount or the property of the defective portion based on the image signal.

The present invention also relates to a method for analyzing a defective portion present on a target substrate by using a scanning electron microscope.
Based on the position coordinates of the defective part existing on the target substrate mounted on the stage, the defective part is located in a wide imaging field of view, and a pseudo noise component is generated from the background for the located defective part. Scanning and irradiating the electron beam so as to obtain the wide imaging field of view by controlling to suppress,
An analog image signal is detected from the detector, the detected analog image signal is converted into a low-magnification digital image signal by an A / D converter, and the analog image signal is converted into a low-magnification digital image signal indicating the defective portion. A position specifying step of specifying the position of the defective part, and positioning the defective part in a narrow imaging field of view based on the position of the defective part specified by the position specifying step. Scanning and irradiating the beam so that the narrow imaging field of view can be obtained in a focus state, detecting an analog image signal from a detector,
The detected analog image signal is converted into a high-magnification digital image signal by an A / D converter, and the characteristic amount or the property of the defect is determined based on the converted digital image signal indicating the high-magnification defect. Analysis step of analyzing. The present invention also provides a method for analyzing a defective portion present on a target substrate by using a scanning electron microscope, wherein the defective portion is located based on the position coordinates of the defective portion present on the target substrate mounted on a stage. Is positioned within a wide imaging field of view, and the electron beam is scanned and irradiated so as to obtain the wide imaging field by controlling the spot diameter on the basis of background information with respect to the located defective portion, and an analog image is obtained from the detector. A signal is detected, the detected analog image signal is converted into a low-magnification digital image signal by an A / D converter, and the position of the defect is determined based on the converted digital image signal indicating the low-magnification defect. Positioning the defective part in a narrow imaging field of view based on the position specifying step of specifying the defective part and the position of the defective part specified by the position specifying step. The camera is scanned and irradiated so that the narrow imaging field of view is obtained in a focused state, an analog image signal is detected from a detector, and the detected analog image signal is converted into a high-magnification digital image signal by an A / D converter. And analyzing the characteristic amount or the property of the defective portion based on the converted digital image signal indicating the high-magnification defective portion.

According to the present invention, there is provided a method for analyzing a defective portion existing on a target substrate by using a scanning electron microscope.
Positioning the defect site within a wide imaging field of view based on the position coordinates of the defect site present on the target substrate mounted on the stage, and applying an electron beam to the located defect site in the wide imaging field of view. Is scanned and irradiated so as to obtain an analog image signal from a detector, and performs a signal processing on the detected analog image signal in accordance with the background state of the defective portion, thereby generating a high-frequency pseudo-noise component due to the background. The analog image signal in which the high-frequency pseudo-noise component is reduced is converted into a low-magnification digital image signal by an A / D converter. A position specifying step of specifying the position of the defective part, and positioning the defective part in a narrow imaging field of view based on the position of the defective part specified by the position specifying step. The focused defect is irradiated with an electron beam in a focused state so that a narrow imaging field of view can be obtained by scanning, an analog image signal is detected from a detector, and the detected analog image signal is converted by an A / D converter. Converting the digital image signal into a high-magnification digital image signal, and analyzing the characteristic amount or the property of the defect site based on the converted digital image signal indicating the high-magnification defect site. Further, the present invention provides a method for analyzing a defect site present on a target substrate by a scanning electron microscope,
Positioning the defect site within a wide imaging field of view based on the position coordinates of the defect site present on the target substrate mounted on the stage, and applying an electron beam to the located defect site in the wide imaging field of view. Is scanned and illuminated so as to obtain an analog image signal from a detector, and the detected analog image signal is converted into a low-magnification digital image signal by an A / D converter, and the converted low-magnification digital image signal is obtained. Performing signal processing on the digital image signal according to the background state of the defect site to reduce high-frequency pseudo-noise components due to the background,
A position specifying step of specifying the position of the defective part based on a digital image signal indicating a low-magnification defective part in which the high-frequency pseudo noise component is reduced, and a position of the defective part specified by the position specifying step. The defective portion is positioned in a narrow imaging field of view, and the located defective portion is scanned and irradiated with an electron beam so as to obtain a narrow imaging field of view in a focused state, and an analog image signal is detected from a detector. The detected analog image signal is converted into a high-magnification digital image signal by an A / D converter, and the characteristic amount or the property of the defect is analyzed based on the converted digital image signal indicating the high-magnification defect. And an analyzing step.

Further, according to the present invention, in the position specifying step in the method for analyzing a defective portion by the scanning electron microscope, a digital image signal indicating a low-magnification defective portion and a reference digital image signal having no low-magnification defective portion are obtained. The method is characterized in that the position of a defective portion is specified by extracting a difference image signal. Further, the present invention is characterized in that in the position specifying step in the defect site analysis method using the scanning electron microscope, a digital image signal indicating a low magnification defect site is displayed on a display device. Also, the present invention
In the position identification step in the defect site analysis method using the scanning electron microscope, the position coordinates of the defect site present on the target substrate mounted on the stage are acquired from a visual inspection device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a scanning electron microscope according to the present invention will be described with reference to the drawings. The manufacturing process of a semiconductor wafer or the like according to the present invention extends to several hundred processes, and pattern defects and attached foreign substances (collectively referred to as defects) generated in each process are found at an early stage, and countermeasures are taken at an early stage. Doing so is important for improving yield. For this reason, inspections for defects such as pattern defects and adhered foreign substances generated on a wafer (substrate) during a manufacturing process are performed using an optical appearance inspection apparatus or an optical foreign substance inspection apparatus. Since the optical appearance inspection apparatus inspects a defect such as a pattern defect or an adhering foreign substance existing on a substrate such as a wafer and detects the number of the defect and a position in the substrate, these optical defect inspection apparatuses are used. It was difficult to estimate the cause of the defect. Therefore, in order to estimate the cause of these defects, it is necessary to visually check (review) them.

However, when the number of defects per one substrate (wafer) is more than one hundred to several thousand, it is practically impossible to manually perform the review anymore. Therefore, there is a need for a microscope according to the present invention that automatically captures a defect image at the coordinate position using the defect coordinates detected by the inspection apparatus, that is, has a function of automatically collecting defect images. . Therefore, as a microscope having a function of automatically collecting defect images according to the present invention, an i-line capable of observing a defect having a size on the order of several nanometers to a micron or an ultraviolet light having a shorter wavelength than that (e.g., excimer laser light) An optical microscope using an electron microscope or the like is used. Then, in a microscope having a function of automatically collecting the defect images, based on a high-resolution appearance defect image of a target substrate such as a semiconductor wafer, a detailed analysis is performed and the state of the manufacturing process (particularly, the state of occurrence of defects, that is, (Defect category) must be automatically classified and determined.

Next, an embodiment using an electron beam type microscope as a microscope having an automatic defect image collecting function according to the present invention will be described with reference to FIGS. FIG.
1 is a schematic configuration diagram showing a first embodiment of a scanning electron microscope 1201 having a function of automatically collecting defect images according to the present invention. That is, the optical appearance inspection device 12 shown in FIG.
03, a defect such as a pattern defect or an attached foreign substance is inspected, and the number of the defects and the position in the substrate are detected.
That is, a target substrate (sample) 107 for automatically classifying and determining a defect category) is loaded and the stage 10
6 will be mounted. In addition, in order to automatically classify and determine the state of the manufacturing process (especially, the state of occurrence of a defect, that is, the category of a defect), feature amounts (defect size, defect surface state, defect It is necessary to create teaching data for teaching the category of a defect on the basis of the gray value obtained from the above, the color information of the defect, and the like. Therefore, in order to acquire the teaching appearance defect image in advance, the target substrate having the teaching appearance defect is also loaded and placed on the stage 106.

The scanning electron microscope 1201 having a function of automatically collecting defect images according to the present invention comprises a detection optical system 100.
, A control system 200, and an electron beam image extracting unit 300. The detection optical system 100 includes an electron gun 101,
A converging lens 103 for converging an electron beam 102 emitted from an electron gun 101, a deflection coil 104 for deflecting the electron beam 102, an objective lens 105 for condensing the electron beam into a spot, and A stage 106 on which the target substrate 107 is mounted, a detector 112 for detecting secondary electrons, reflected electrons, or absorbed electrons 111 or the like generated from the target substrate 107, and a secondary electron detected by the detector 112 The signal amplifier 114 amplifies a signal of reflected electrons or absorbed electrons.

The control system 200 controls the driving of the stage 106 in the xy axis direction based on the stage control signal 204 obtained from the overall control unit 210, and controls the beam spot diameter control unit 2
The stage drive control unit 110 controls the drive of the stage 106 in the z-axis direction (height direction) based on the beam spot diameter control signal obtained from the control unit 03, and the electron beam generated by the deflection coil 104 and the like based on a command from the overall control unit 210. A deflection control unit 108 that controls the frequency and deflection width of beam deflection and two-dimensionally scans the electron beam 102 on the target substrate 107, and a numerical aperture of the objective lens 105 based on a command from the overall control unit 210. And information on the target substrate (sample) 107 input to the overall control unit 210 and inspection information such as position coordinates of defects inspected and detected by the visual inspection device 1203 are stored. Sample information / inspection information storage unit 201, information on target substrate (sample) stored in the sample information / inspection information storage unit 201, and appearance inspection apparatus 1 The electron beam 102 on the basis of the error or the like between the coordinate system and the coordinate system of an electron microscope at 03 according to the range of two-dimensionally scanned on the target substrate 107 detector 112
Imaging magnification setting unit 202 for setting the imaging magnification of secondary electrons, reflected electrons, or absorption electrons imaged by the imaging unit, and the imaging magnification of the secondary electrons, reflected electrons, or absorption electrons set by the imaging magnification setting unit 202 and the sample The information on the target substrate (sample) stored in the information and inspection information storage unit 201, the information on the sampling method obtained from the A / D conversion unit 116, and the information detected by the stage drive control unit 110 obtained from the overall control unit 210 Stage 10
A beam spot beam diameter on the sample surface optimal for imaging is determined based on the x-y-z position information of No. 6 and a command for controlling the deflection control unit 108 and the objective lens 109 to generate a spot diameter control signal. Beam spot diameter control unit 2
03 and the overall control unit 210.

The electron beam image extraction unit 300 converts the analog signal of secondary electrons, reflected electrons, or absorbed electrons, which is amplified and output from the signal amplification unit 114, into the deflection control unit 10.
A / D converter that performs A / D conversion into a digital signal in synchronization with the deflection control signal obtained from step 8, and provides information on a sampling method including period information T and the like at the time of digital sampling to the beam spot diameter controller 203. 116
And a frame memory 117 for temporarily storing the digital electron beam image converted by the A / D conversion unit 116, and integrating and subtracting the image stored in the frame memory 117 and storing the image again in the frame memory 117. CPU
An image processing unit 12 having an arithmetic unit configured from the above and the like, and a D / A conversion unit 118 that converts a digital electron beam image stored in the frame memory 117 into an analog electron beam image.
0, a display device 115 for displaying an analog signal of secondary electrons, reflected electrons, or absorbed electrons amplified and output from the signal amplifier 114 and an analog electron beam image obtained from the D / A converter 118; Memory 1
The image storage unit 119 includes an optical disk, a magnetic disk, and a semiconductor memory for storing and storing the digital electron beam image stored in the storage unit 17. The arithmetic unit of the image processing unit 120 captures an image of the same portion a plurality of times by the detector 112 by scanning the same portion a plurality of times with the electron beam in order to improve the SN ratio of the obtained image, An integration process is performed by using the average value of the plurality of images as an image of the site, or when a high-magnification digital electron beam image is detected, a high-magnification digital electron beam image having a defect and a high-magnification digital electron beam image having no defect are present. It also has a function of comparing a digital electron beam image with a magnification to extract a difference image indicating a defect.

The sample information and inspection information storage unit 201 stores a sample 107 to be imaged obtained by being input to the overall control unit 210 through a keyboard, a recording medium, a network, or the like.
It has a function of storing the information of the inspection and the inspection information. Sample 107
Information includes, for example, sample type, material, color, shape, pattern,
The sample (substrate) shown in Fig. 2
The overall control unit 210 can input and acquire from a production line management system 1205 that manages a production line that manufactures the product or a CAD system 1206 that has design information via a network 1204 or a recording medium. Become. The pattern of the sample includes information such as the presence / absence of a pattern formed on the surface of the sample, the presence / absence of the periodicity of the pattern, and the period of the periodic pattern. If the sample 107 has a different pattern or color for each manufacturing process such as a semiconductor wafer, the manufacturing process name can be included as information obtained from the manufacturing line management system 1205. In addition, when position information of the imaging part in the sample 107 is predetermined, the position information is also included. These pieces of sample information may be design values predetermined for the sample or values of position coordinates of a defect detected by another optical appearance inspection device 1203. Alternatively, the value may be a value extracted by performing arbitrary processing on the analog data or digital data acquired by the image processing unit 120. For example, a frequency component of a detection signal obtained from the image processing unit 120 by performing a Fourier transform process on the obtained digital data can be included in this value.

In the imaging magnification setting section 202, a magnification for imaging the sample 107 is set. This magnification may be a value given to the imaging magnification setting unit 202 from the outside of the scanning electron microscope according to the present invention, or the sample information storage unit 2
The value may be a value obtained based on the information of the sample stored in 01. As the imaging magnification, for example, a high magnification for obtaining a digital image having a high resolution for detailed analysis of a defective portion (for example, 30,000 to 6 times or more of about 10,000 times or more)
In the case of 10,000 times, the visual field becomes about 1 to 2 μm and 0.1 μm
Can be recognized as about 3 mm to 6 mm. ) And a low magnification (for example, 10,000 times or less, about 10,000 times or less, which can specify the position of the defective portion, the field of view is several tens μm to about 10 μm, and a coordinate system in various kinds of visual inspection devices and a coordinate system in an electron microscope. And a defect of 0.1 μm can be recognized as about 1 mm). A beam spot diameter control unit 203 is a beam spot diameter on a sample surface optimal for imaging based on information on sampling in the sample information and inspection information storage unit 201, the imaging magnification setting unit 202, and the A / D conversion unit 116. Has the function of determining The information on the sampling provided from the A / D converter 116 is, for example, cycle information at the time of digital sampling. A / D converter 1
When sampling and quantizing at 16, the sampling period T is described as being constant between the case of imaging at low magnification and the case of imaging at high magnification. However, the case of imaging at low magnification and imaging at high magnification is described. Thus, the sampling period T may be changed. When changing the sampling period T in the A / D converter 116, the sampling period T may be changed based on the beam spot diameter control signal output from the beam spot diameter controller 203.

Next, a scanning electron microscope 1201 is used as a microscope based on the defect coordinates on the target substrate which is input from the optical appearance inspection apparatus 1203 to the overall control unit 210 through a network or a recording medium and given. The automatic collection of images by using the method will be described with reference to FIG. First, in step S301, a set of coordinates of a large number of defective sites detected and detected by the optical appearance inspection device 1203 with respect to the plurality of target substrates 107 to be input to the scanning electron microscope 1201 is stored in the overall control unit 210.
To the sample information and inspection information storage unit 201
Is stored. Next, in step S302, the overall control unit 210 stores the position coordinates of one of the defect sites on the target substrate 107 loaded and placed on the stage 106 into the sample information and inspection information storage unit. Selected from 201 and read.

Next, in step S303, the overall control unit 210 issues a command to the stage drive control unit 110 to move the stage 106 in order to capture an electron beam image at the selected coordinate portion on the target substrate 107. The position of the defect site selected by moving is roughly positioned on the optical axis of the electron beam 102. Next, in step S304,
After the stage 106 is moved and positioned, the overall control unit 2
10 controls the deflection control unit 108 so that the detector 112 can image the low-magnification electron beam image set by the imaging magnification setting unit 202, and controls the electron beam 102 on the target substrate 107 of the electron beam 102. The dimensional scanning width is increased to about several to about 10 μm. At the same time, the beam spot diameter control unit 203 adjusts the beam spot so that the electron beam image detected by the detector 112 does not include a high-frequency noise component corresponding to the low magnification set by the imaging magnification setting unit 202. A spot diameter control signal is provided to the stage drive control unit 110 to raise the stage 106 in the z-direction.
As shown in FIG. 3B, the electron beam 102 is defocused and irradiated on the defect site on the target substrate 107 with the beam spot diameter enlarged to 404. The detector 112 detects the noise component at a low magnification at the defect site. Are captured, converted into digital electron beam images by the A / D converter 116, and stored in the frame memory 117. The low magnification referred to here means that the defect site has a low magnification field of view (about several to 10 μm) according to the error between the coordinate system of the various types of visual inspection devices 1203 and the coordinate system of the electron microscope 1201.
) Is set as the imaging magnification up to about 10,000 times. Thus, when the low magnification is set to about 10,000 times, the visual field becomes about several to about 10 μm.
Defects of 1 μm can be recognized to about 1 mm.

Next, in step S 305, the overall control section 210 executes the stage drive control section 110 based on the sample information and the sample information stored in the inspection information storage section 201.
, The stage 106 is moved to position a defect-free part having the same background as the defect part on the optical axis of the electron beam 102. Then, the same 2 as in step S304
A non-defective part is irradiated with the electron beam 102 in a defocused state with a two-dimensional scanning width (low magnification), and an electron beam image with no noise component at a low magnification in the non-defective part is captured by the detector 112. The image is converted into a digital electron beam image by the / D conversion unit 116 and stored in the frame memory 117. For example, in a semiconductor product, since a plurality of chips having the same structure are arranged on the wafer and the pattern is formed, for example, an electron beam image of the same portion of an adjacent chip is taken. Is done. If an electron beam image of a non-defective part having the same background as the defective part can be acquired in advance and stored in a storage device (eg, 119) such as a memory installed inside or outside the microscope, step S305 is performed. Can be eliminated. Next, in step S506, the image processing unit 120 relatively aligns the electron beam images not including the two noise components captured in step S304 and step S305 to extract a difference image, and extracts the difference image. In the difference image, a portion where a difference occurs can be recognized as a defective portion.
For example, by displaying the extracted difference image on the display device 115, the defect site can be recognized. By feeding back the coordinates of the recognized defect site to the overall control unit 210, the overall control unit 210 can be recognized. Indicates the position of a defect that is imaged and recognized at a low magnification with an electron beam 10.
It is possible to accurately position on the two optical axes. The recognition of the coordinates of the defective portion by the low magnification is performed by the image processing unit 1.
20 may be executed by the calculation unit. The display device 11
By designating a defective portion with a low magnification displayed on the screen 5 on the screen, its position coordinates can be output from the display device 115 and provided to the overall control unit 210.

Next, in step S 507, the overall control unit 210 determines whether the image processing unit 120 or the display device 115
Based on the position coordinates of the defect site recognized based on the low-magnification electron beam image obtained from the above, the stage drive control unit 110 is controlled to move the stage 106 to move the defect site to the optical axis of the electron beam 102. Position accurately with an accuracy of about 1 μm or less. The overall control unit 210 controls the deflection control unit 108 so that the detector 112 can capture the high-magnification electron beam image of, for example, about 30,000 to 60,000 set by the imaging magnification setting unit 202, and The two-dimensional scanning width of the electron beam 102 on the target substrate 107 by the beam 102 is reduced to about 1 to 2 μm or less. At the same time, the beam spot diameter control unit 203 controls the beam so as to capture an ultra-fine electron beam image having a high resolution capable of faithfully calculating the feature amount of the defect corresponding to the high magnification set by the imaging magnification setting unit 202. The spot diameter control signal is provided to the stage drive control unit 110 to lower the stage 106 in the z-direction so that the electron beam 102 is focused on the defect site on the target substrate 107 as shown in FIG. Irradiate,
The detector 112 captures an ultra-fine electron beam image having high resolution and high resolution at the defect site, and the A / D converter 1
The image is converted into a digital electron beam image at 16 and the frame memory 1
17 is stored. The high magnification here is an imaging magnification of 10,000 times or more (for example, about 30,000 to 60,000 times) at which a high-resolution digital electron beam image can be obtained. When the imaging magnification is set to a high magnification of, for example, 30,000 to 60,000, a defect of 0.1 μm can be recognized at about 3 mm to 6 mm, and a defect of 0.05 μm can be recognized at about 1.5 mm to 3 mm. A digital electron beam image having a high resolution, and based on the obtained digital electron beam image having a high resolution, feature amounts (size, shape, surface state, gray value, etc.) of a defective portion
Can be extracted for detailed analysis.

As described above, since the defect site inspected and detected by the visual inspection device 1203 is positioned in the coordinate system of the electron microscope, the defect site can be positioned within a field of view with a high magnification of 10,000 times or more. As a result, it is possible to capture an ultra-fine electron beam image having a high resolution and a high resolution including a defective portion. Furthermore, since it is possible to capture an ultra-fine electron beam image having a high resolution and a high resolution including a defect portion, the defect feature amounts (size, shape, The surface condition, the gray value, etc.) are extracted, and the defect category (the cause of the defect occurrence is estimated) based on this characteristic amount and the teaching data (relationship between the representative defect characteristic amount and the defect category) taught in advance. Can be classified). Next, in step S308, the overall control unit 210 captures electron beam images for all defect sites based on the sample information and the inspection information stored in the inspection information storage unit 201 that have been inspected by the visual inspection device 1203. It is confirmed whether or not the process has been completed. If data to be imaged still remains, the process returns to step S302. If all the images have been captured, the automatic collection of images ends.

In the above automatic image collection, step S
First, at 304, a defective part is imaged at a low magnification and the position of the defective part is extracted by the coordinate system of the electron microscope. Then, at step S307, the part is imaged at a high magnification. Originally, based on the position of the defect coordinates given by the visual inspection device,
The purpose of acquiring an ultra-fine electron beam image of a defective part is achieved only by imaging at a high magnification with an electron microscope, but here the reason for capturing an image at a high magnification after once capturing an image at a low magnification Since there is an error between the coordinates given from the visual inspection device 1203 and the coordinates used to determine the movement of the stage 106 and the imaging visual field used in the electron microscope 1201, the defect coordinate position from the visual inspection device 1203 This is because there is no guarantee that a defective portion will be included in the field of view even if an attempt is made to image at high magnification. Therefore, taking into account the error between the coordinate system of the visual inspection device 1203 and the coordinate system of the electron microscope 1201, the imaging magnification setting unit is set based on the sample information and the inspection information stored in the inspection information storage unit 201. In 202, by determining and setting the imaging magnification at a low magnification in the electron microscope 1201, when the target substrate 107 having a defective part is put on the stage 106 of the electron microscope 1201 and placed, the defective part is removed. It can be positioned within a low magnification imaging visual field (about several to about 10 μm).

In step S306, the difference between the electron beam image at a low magnification and containing no noise component at a low magnification and the electron beam image at a low magnification and without a noise component at a defect-free site in the same background as the defect site is determined. The reason why the image is calculated by the image processing unit 120 is that by performing the difference image calculation of the two images of the same background part, the difference part is easily recognized as a defective part, and the position of the defective part is electronically determined. This is because it can be extracted and specified in the coordinate system of the microscope. In step S306, the difference image calculation performed by the image processing unit 120 is performed using the two-dimensional digital image obtained by performing analog-to-digital conversion on the electron beam image detected by the detector 112 using the A / D conversion unit 116. Is When the A / D converter 116 converts an analog signal into a digital signal, the frequency component w of the analog signal and the sampling interval T at the time of digital sampling satisfy the sampling theorem shown in the following equation (1). Otherwise, an analog image signal including information on a defective portion detected by being imaged at a low magnification cannot be accurately converted to a digital image signal without generating a pseudo noise component. The reason for this is that digital noise converted under conditions that do not satisfy the sampling theorem includes pseudo noise generally called moiré. Therefore, when the difference image processing is performed in step S306 in a state where such noise is included, the possibility that the portion where the difference in the electron beam image has occurred due to the noise is likely to be erroneously recognized as a defective portion is increased. As a result, there may be a case where the defect site cannot be specified in the electron beam coordinate system, and in step S307, a high-magnification electron beam image of the defect site cannot be obtained accurately.

Here, the sampling theorem means that a frequency component contained in an analog signal component before digital conversion is represented by w,
It is a theorem that when the sampling interval at the time of sampling is T, it is necessary to satisfy the condition of the following (Equation 1). That is, this is the relationship between the frequency component w of the detected analog signal and the digital sampling interval T. T <1 / 2w (Equation 1) When imaging a defect generated in a manufacturing process of a semiconductor or the like with a scanning electron microscope, the frequency components of the detected analog signal are related to the observation target (substrate 107 to be observed),
That is, the frequency component of the pattern of the semiconductor wafer itself and the beam diameter when the surface of the pattern is detected by the electron beam.
In the scanning electron microscope 1201, if the electron beam diameter on the surface of the sample 107 is approximately the same size as the fine unevenness of the pattern, an analog signal detected by the detector 112 will not be included in the analog signal. Although the same frequency components as the irregularities are superimposed, if the beam diameter on the surface of the sample 107 is sufficiently large compared to the irregularities of the pattern, the detected analog signal will have the same level of fine irregularities as the pattern. No frequency components are superimposed. This means that based on the beam spot diameter control signal from the beam spot diameter control unit 203, the electron beam diameter on the surface of the sample 107 becomes much larger than the frequency component of the pattern on the surface of the sample to be imaged. By performing such control, that is, defocusing (blurring) as shown in FIG. 6B and capturing an electron beam image by the detector 112, the frequency component of the detected analog signal is reduced by the pattern of the surface of the sample. It has only a very low frequency component as compared to the frequency component it has, and it is possible to capture an image under the condition satisfying the above (Equation 1). Therefore, it is possible to position the defect site detected in the coordinate system of the visual inspection device 1203 in the low magnification imaging visual field in the electron microscope 1201 and to recognize the position of the defect site in the coordinate system of the electron microscope 1201. Can be specified.

However, if the degree of defocus is too large, the signal component of the defective portion to be extracted will not be detected by the detector 112. FIG. 4 is a diagram schematically illustrating this state. FIG. 4A is a cross-sectional view showing one embodiment of a sample surface to be detected. FIG. 4 (b)
(C) shows the waveform of the analog signal detected from each of the same portions, and (b) shows the waveform of the analog signal detected when the electron beam diameter on the sample surface is almost equal to the size of the surface irregularities. (C) shows a waveform of an analog signal detected by controlling the diameter of the electron beam on the sample surface to be very large with respect to the size of the surface irregularities. FIG. 4 (a)
3 shows a sample 107 in which a pattern portion 401 is formed on a base portion 402 and a defect 403 such as a foreign substance is attached on the base portion 402. Looking at the waveform shown in FIG. 4B, a peak of the waveform due to detection of the defect 403 such as a foreign substance is observed. The reason why the voltage value of the portion corresponding to the edge portion of the pattern 401 is higher than the surrounding voltage value is that an edge effect specific to the detection waveform of the scanning electron microscope appears. As shown in FIG. 4C, in a state in which defocus is excessively performed, the pattern 40
It can be seen that the frequency component corresponding to the frequency component of the fine unevenness of No. 1 is not superimposed on the detection signal, and as a result, it is not possible to observe with the deterioration of the waveform of the signal component that has detected the defective portion 403 such as a foreign substance. Even if the analog signal detected by the detector 112 is converted into a digital signal by the A / D converter 116 in such a state, it is difficult for the image processor 120 to detect the above defect by the digital signal processing. . The size of the defect to be detected is usually 1/2 to 1/3 of the minimum dimension of a pattern formed on the semiconductor product, and is 0.2 to 0.2.
It is about 0.05 μm. Therefore, in order to determine the beam spot diameter in the defocus state necessary for detecting a defect to be targeted while satisfying the sampling theorem in the beam spot diameter control unit 203, sample information and inspection information are required. It is necessary to take into account sample information such as the pattern size and the pattern cycle stored in the storage unit 201.

Next, a digital sampling interval for sampling and quantizing in the A / D converter 116 will be described. That is, the A / D converter 116 determines how many digital data to sample one scan of the beam scanning based on the control of the deflection controller 108 for the deflection coil 104. This is determined as the device specification of the electron microscope. For example, when sampling 512 times, the number of pixels of the obtained digital image in the scanning direction is 512 pixels. However, the scanning width controlled by the deflection control unit 108 based on a command from the overall control unit 210 is different from the imaging magnification setting unit 202.
Is determined by the magnification of the image set in. In the case of low magnification, since a relatively large area (about several to 10 μm) is scanned in one scan compared to the case of high magnification,
This is because even if the number of times of sampling is constant, the interval of the sampled data on the target substrate is widened. In other words, regarding the digital sampling interval,
The imaging magnification is an important item. In any case, the low-magnification imaging magnification is determined by various types of visual inspection devices 1203.
Is input to the overall control unit 210 in accordance with an error between the coordinate system of the electron microscope 1201 and the coordinate system of the electron microscope 1201 and is reduced to about 10,000 times or less (divisor number to 1
(About 0 μm). That is, since the target substrate 107 having a defective portion inspected and detected by various types of appearance inspection devices 1203 is put into the electron microscope, the imaging magnification of the low magnification in the electron microscope 1201 is:
When the position is determined in the coordinate system of the electron microscope based on the coordinate data of the defective portion on the target substrate 107 inspected and detected by various types of visual inspection devices, the defective portion is positioned in the low magnification field of view. Is determined as follows. Therefore,
When an image of a defective portion on the target substrate 107 loaded and mounted on the stage 106 of the electron microscope is taken at a low magnification, a digital image signal indicating the defective portion is obtained, and the position coordinates of the defective portion are converted into the coordinate system of the electron microscope It is possible to locate the defective part in the field of view with high magnification, obtain a high-resolution digital image signal with high magnification, and perform detailed analysis on the defective part.

In the automatic collection of images shown in FIG. 3, in steps S304 and S307, the same part is imaged at different magnifications using an electron microscope. Further, since a different pattern is formed for each product on the target substrate 107, the pattern cycle and the pattern size also differ. Therefore, in order to accurately perform A / D conversion and extract a defective area in an electron microscope,
(1) frequency components of the surface pattern of the target substrate,
(2) electron beam diameter on the surface of the target substrate at the time of imaging,
(3) Control must be performed so that the three items of imaging magnification satisfy the sampling theorem based on the above equation (Equation 1). As described above, the beam spot diameter control unit 203 determines (1) the frequency component of the surface pattern of the target substrate obtained from the sample information and inspection information storage unit 201 and (3) the result set by the imaging magnification setting unit 202. Image magnification (especially low magnification)
(2) Determine the electron beam diameter on the surface of the target substrate when imaging is performed at a particularly low magnification based on the sampling interval in the A / D converter 116 and the stage based on the determined beam spot diameter control signal 205. Drive control unit 110
And irradiating the electron beam in a defocused state on the surface of the target substrate, thereby satisfying the sampling theorem based on the above equation (1) and imaging at a low magnification without generating a noise component to indicate a defective portion. Images can be acquired.

Next, a method of capturing an electron beam image of the target substrate (sample) 107 without generating a noise component will be described. FIG. 6A shows an image pickup area 3 when the sample 107 is picked up by the scanning electron microscope.
01 and FIG. 6B show a two-dimensional digital image 302 of the imaging area 301. Area sizes xw and yw in the x and y directions of the imaging area 301 indicate the size of an area where the electron beam 102 is scanned on the sample 107 by the deflection coil 104. The two-dimensional digital image 302 obtained from the A / D conversion unit 116 has M,
It is assumed that there are N pixels. When obtaining a two-dimensional digital image 302 of the imaging area 301, in the x direction, a one-dimensional analog electric signal obtained from one scan of the electron beam 102 over a distance xw is digitally sampled into M digital data. In the y direction, scanning of the electron beam 102 over the distance xw is performed N times with respect to the distance yw in the y direction. This means that the analog electric signal detected from the sample 107 in each of the x and y directions is converted into M and x in the x and y directions, respectively.
This means that the data is sampled as N data. In this case, in order to accurately image the two-dimensional digital signal 302, the analog electric signal of the intensity distribution of the secondary electrons emitted from the sample 107 is converted. It is necessary to satisfy the sampling theorem (Equation 1) between the frequency component and the sampling interval. If digital sampling is performed under conditions that do not satisfy the sampling theorem, a two-dimensional digital image obtained will contain noise.

Assuming that the number of pixels (M, N) to be sampled is constant irrespective of the imaging magnification, the scanning area xw,
When yw is large, that is, when the imaging magnification is large, the spatial cycle of digital sampling is larger than when the scanning area xw, yw is small, that is, when the imaging magnification is small. This means that control must be performed so that the sampling theorem is established between the frequency component of the analog electric signal of the secondary electron intensity distribution and the sampling interval according to the change in the imaging magnification. In this control, (A) secondary electrons are detected such that components higher than the frequency determined by the sampling theorem are not included in the detected analog electric signal. (B) The frequency determined by the sampling theorem from the detected analog electric signal There are two methods of removing higher frequency components. The method (B) will be described later with reference to FIG. 10. Here, the method (A) will be described. FIG. 6 shows the state of electron beam irradiation on the sample 107. In FIG. 6A, the sample 1
On 07, the electron beam 102 is converged in a substantially point-like manner. The secondary electron intensity distribution detected in such a beam shape includes a high-frequency component corresponding to a fine shape or the like on the sample. On the other hand, FIG.
The state where the stage 106 is moved in the z direction from the state of FIG. In this case, the electron beam 102 is not sufficiently converged on the surface of the sample, and the beam spot diameter 404 on the sample has a larger value than in the case of FIG. The analog electric signal of the secondary electron intensity distribution detected when the image is captured in this state does not include high frequency components corresponding to the minute shape of the surface of the sample, and the captured image is defocused (blurred). Image. As described above, by controlling the beam spot diameter of the electron beam on the sample and performing imaging in a defocused state, it is possible to reduce high frequency components of the obtained secondary electron signal intensity distribution. That is, if the beam spot diameter is controlled to have an arbitrary size, it is possible to prevent a component having a frequency higher than the arbitrary frequency from being included in the analog electric signal obtained by converting the detected secondary electrons. .

FIG. 7 shows a sequence in which imaging is performed without generating noise using the above principle in the embodiment of the present invention shown in FIG. First, step S70
In 1, an imaging magnification is set in the imaging magnification setting unit 202. As described above, the set value may be calculated from the contents of the sample information and the test information storage unit 201, or may be directly input by a user from the outside. Next, in step S702, the beam spot diameter control unit 203 uses the imaging magnification set by the imaging magnification setting unit 202 and information on the sampling method obtained from the A / D conversion unit 116 to satisfy the sampling theorem. Is determined for defocus imaging. The conditions include the value of the beam spot diameter on the sample surface and the amount of movement of the stage 106 for imaging with the beam spot diameter. Next, step S703
, The stage 106 is moved in the z direction based on the control by the stage drive control unit 110 using the beam spot diameter control signal so as to capture an image under the determined conditions. Then, in step S704, the overall control unit 2
10 controls the deflection coil 104 by the deflection control unit 108 according to the imaging magnification set by the imaging magnification setting unit 202 to irradiate the electron beam 102 to the surface of the sample 107 in a two-dimensional scanning range. An electron beam image is captured by the detector 112 at the above-described imaging magnification.

When a periodic pattern is formed on the sample 107 to be imaged, the analog electric signal detected by the detector 112 includes the frequency of the pattern on the sample depending on the imaging magnification. The beam spot diameter control unit 203 sets the information on the pattern of the imaging target stored in the sample information and the inspection information storage unit 201 and the imaging magnification setting unit 202 because the frequency component due to By using the information on the imaging magnification and the sampling interval obtained from the A / D conversion unit 116, it is possible to determine the imaging conditions for satisfying the sampling theorem for samples of various patterns. In other words, the beam spot diameter control unit 203 controls the beam spot diameter so as to satisfy the sampling theorem even when capturing any object at any magnification, thereby enabling accurate imaging without generating pseudo noise. . Next, a second embodiment of the scanning electron microscope for automatically collecting defect images according to the present invention will be described with reference to FIG. In the second embodiment, a method of controlling the spot diameter of the electron beam 102 on the sample 107 is not based on the movement of the stage 106 in the z direction as shown in the first embodiment in FIG. A method of changing the characteristics of the objective lens 107 used to focus the beam 102 on the sample 107 is used. Other configurations of the second embodiment are the same as those of the first embodiment shown in FIG. That is, the beam spot diameter control unit 203 determines an imaging condition that satisfies the sampling theorem, and performs image capturing under such a condition.
09 to change (control) the numerical aperture of the objective lens 109 using the objective lens control signal 206.
By changing the numerical aperture of the objective lens 109, the electron beam spot diameter 404 on the surface of the sample 106 can be increased as shown in FIG. 6B, and an electron beam image can be taken in a defocused state. It becomes possible.

Next, a third embodiment of the scanning electron microscope for automatically collecting defect images according to the present invention will be described with reference to FIG. In the third embodiment, the beam current of the electron beam 102 emitted from the electron gun 101 is controlled in order to image the sample 107 in a defocused state. Other configurations of the third embodiment are the same as those of the first embodiment shown in FIG. When the beam diameter of the electron beam 102 is d and the beam current is i, the following equation (2) is established. This indicates that the electron beam spot diameter on the surface of the 107 sample is increased by increasing the beam current of the electron beam 102. d = K × i (Equation 2) where K is a constant. In other words, the beam spot diameter control unit 203 controls the beam current emitted from the electron gun 101 using the electron gun control signal 207 so as to increase the beam current, so that the surface of the sample 106 as shown in FIG. By increasing the electron beam spot diameter 404 above, it is possible to capture an electron beam image in a defocused state. Also, by increasing the beam current in this way, it is possible to obtain the advantage that beam scanning can be performed at a high speed.

Next, a fourth embodiment of the scanning electron microscope for automatically collecting defect images according to the present invention will be described with reference to FIG. In the first, second and third embodiments,
When imaging at low magnification, the electron beam 102 is defocused and imaged on the sample 107 so that the detected analog electric signal of the intensity distribution of the secondary electrons does not include a frequency component higher than a certain frequency. And obtains a low-magnification digital image signal indicating a true defect portion containing no noise component from the A / D conversion section 116 to specify the position of the defect portion in the low-magnification field of view. Was. On the other hand, in the fourth embodiment shown in FIG. 10, the analog signal processing unit 703 removes a frequency component of a predetermined frequency or more from the detected analog electric signal 113 to include a noise component from the A / D conversion unit 116. A low-magnification digital image signal indicating a true defective part is obtained, and the position of the defective part is specified in the low-magnification field of view. In the fourth embodiment, the sample information and inspection information storage unit 201, the imaging magnification setting unit 202, and the A / D conversion unit 116
And a signal processing control unit 702 that determines the content of processing for the detection signal based on this information and an analog signal processing unit 703 that performs analog signal processing. Signal processing control unit 7
02 uses the analog signal processing control signal 701 to instruct the analog signal processing unit 703 to remove a frequency component having a certain frequency or higher from the analog electric signal 122 so as to satisfy the sampling theorem. FIG. 11 shows an embodiment of the analog signal processing unit 703. The analog signal processing unit 703 has one or more frequency filter circuits 802 having different frequency characteristics. The frequency filter circuit 802 is a band-pass (band-pass) analog filter circuit. In response to an instruction from the signal processing control unit 702, the switch control unit 803 changes the connection state of the frequency filter circuits 802 to the switch circuit 80.
4, the filter can be arbitrarily changed, and a filter required for the processing can be selected. Note that in order to realize the same function, instead of a method of selecting a necessary filter circuit from a plurality of filter circuits as in the embodiment shown in FIG. A method of changing the filter characteristics by changing the parameters that determine the characteristics of the circuit (when the filter circuit includes a capacitor, a resistor, and an inductor, the capacitance, the resistance, the inductance, and the like) may be adopted.

Next, a fifth embodiment of the scanning electron microscope for automatically collecting defect images according to the present invention will be described with reference to FIG. In the fifth embodiment, in order to perform digital processing so that pseudo data (pseudo noise) does not occur in an electron beam image captured at a low magnification, the A / D conversion unit 116 performs A / D conversion according to imaging conditions. The object of the present invention is to perform a digital frequency filtering process on the digital data after the / D conversion to obtain a low-magnification digital image signal indicating a true defect portion, and to specify the position of the defect portion in a low-magnification field of view. I have. In the image processing unit 120,
A digital signal processing unit 901 for performing digital signal processing is provided. FIG. 13 illustrates an embodiment of the digital signal processing unit 901. Microprocessor 100 accessible to frame memory 117
3, a program memory 1001 in which a program for processing performed by the microprocessor is stored, and a program control unit 1002 for controlling the microprocessor 1003 to perform processing based on an instruction given from the digital signal processing control signal 903. ing. Program 10
01 stores in advance one or more digital filtering programs having different frequency characteristics. In the embodiment shown in FIGS. 12 and 13, the signal processing control unit 702 includes the sample information and inspection information storage unit 201, the imaging magnification setting unit 202, and the A / Based on information such as the sampling interval from the D conversion unit 116, a program that performs processing on image data in the frame memory 117 is determined,
An instruction is issued using the digital signal processing control signal 903.
The program control unit 1002 receives the instruction of the digital signal processing control signal 903, and
02 selects and starts a program stored in the program memory 1001 to cause the microprocessor 1003 to perform processing as instructed. This makes it possible to perform processing having different filter characteristics according to various imaging conditions. The configuration of the above embodiment is effective even when the program stored in the program memory 1001 is not a filter program.

As described above, when imaging at a low magnification, the electron beam 102 is defocused and applied to the surface of the sample as in the first, second, and third embodiments, and a pseudo noise component is generated. It is more preferable to obtain a digital image indicating a defective portion by controlling the generation so as not to generate the analog image signal from the analog image signal detected or the A / D-converted digital image signal as in the fourth and fifth embodiments. The control is easier than removing the pseudo noise component and obtaining a digital image indicating the defective portion. There are various types of patterns formed on the target substrate, and it is necessary to provide various types of filtering processing in accordance with the types of the patterns, and it is necessary not to delete an image indicating a defective portion. Therefore, in the fourth and fifth embodiments, the filtering process becomes complicated.

Next, in the scanning electron microscope according to the present invention having a function of automatically collecting a defect image, control information for capturing an electron beam image under conditions satisfying the sampling theorem for various products of a semiconductor wafer. (Overall control unit 21
The sample information and inspection information input to 0 and stored in the sample information and inspection information storage unit 201, and the imaging magnification set in the imaging magnification setting unit 202) will be described with reference to FIG. FIG. 14 shows sample information and inspection information input to the overall control unit 210 and stored in the sample information and inspection information storage unit 201, and control information including the imaging magnification set in the imaging magnification setting unit 202 and the like. FIG. 14 (a)
The column of the product name shown in Fig. 7 shows the product name of the semiconductor wafer indicating the type of the sample to be observed in the sample information. In this example, the memory A (the background having a cell pitch of about 5 µm and formed on the surface) The frequency of the pattern is high.) The memory B (the frequency of the background pattern formed on the surface is about 15 μm and the frequency of the background pattern is low). In this case, the frequency of the background pattern is low. The "memory cell presence / absence" column is a field indicating whether or not each product has a memory cell pattern (frequency information of a background pattern at a defective portion related to a sample). "Cell pitch" indicates the cell pitch (design information on a sample) when the product has a memory cell. In the “imaging magnification”, respective magnifications at the time of low magnification and at the time of high magnification are set. Here, the low magnification is approximately several to 10 μm depending on the error between the coordinate system inspected and detected by the visual inspection device and the coordinate system of the electron microscope.
It is determined to be about 10,000 times or less. That is,
There are various pattern inspection apparatuses and foreign substance inspection apparatuses including different manufacturers, and the inspection information includes the model name of the appearance inspection apparatus and the position coordinates of the defective part. In other words, the low magnification is a low magnification (the field of view is approximately several to
(approximately 10,000 times or less so as to be about μm) means an image imaging magnification, and the high magnification is used when performing high-resolution and high-resolution imaging for further detailed analysis of a specified defective portion. (10,000 times or more, for example, about 30,000 to 60,000 times). The magnification at the time of low-magnification imaging is a magnification at which a defect to be imaged can be positioned within the field of view of the low-magnification image, taking into account internal coordinate errors between various types of visual inspection devices and a scanning electron microscope. , Is determined by a user input to the overall control unit 210.

The magnification at the time of high-magnification imaging is determined by taking into consideration the resolution of an image necessary for detailed analysis of a defect.
Is a value determined by inputting by the user. The column of “control condition” is a control condition determined for controlling to capture an image in a state satisfying the sampling theorem from four values of “product name”, “presence or absence of memory cell”, “cell pitch”, and “imaging magnification”. is there. FIG. 14B shows a table showing how the control is specifically performed for each control condition. In this example, the control condition 1 is a condition for focusing and irradiating the surface of the target substrate 107 with an electron beam as shown in FIG.
The beam current is set to 1. [mm] at the z position of the stage.
It means that it is set to 0 [pA]. The control condition 2 is
At the time of low-magnification imaging, as shown in FIG.
7 was irradiated under a condition that the amount of defocusing of the electron beam on the surface was reduced to 10 [mm] and 1.5 [mm], respectively.
An example in the case of setting to [pA] is shown. The control condition 3 is a condition in which the amount of defocusing of the electron beam onto the surface of the target substrate 107 is increased as shown in FIG. An example is shown in which the values are set to 20 [mm] and 2.0 [pA], respectively. In addition, control condition 2,
No. 3 shows a condition in which both the position of the stage in the z-direction and the beam current are increased and the electron beam is defocused on the sample surface and irradiated, but it is clear that either one may be increased. is there. That is, these tables are stored and prepared in a storage device (not shown) in the general control unit 210, the beam spot diameter control unit 203, or the signal processing control unit 702, and the general control unit 21
By referring to these tables, 0 or the beam spot diameter control unit 203 or the signal processing control unit 702 can uniquely determine control conditions for imaging different products at different magnifications.

According to the tables shown in FIGS. 14A and 14B, since both the logic C and the logic D have no memory cells in their patterns, the control condition is “control” regardless of whether the imaging magnification is low or high. Condition 1 ". This is because, since there is no memory cell portion in the circuit pattern, the electron beam image is picked up by the detector 112 and the A / D conversion portion 116 indicates that A / D conversion can be performed. The memory A and the memory B both have memory cells as their patterns, but there are differences in the cell pitch. Therefore, the control condition 1 when imaging the memory A with a small cell pitch at a low magnification is larger than the control condition 2 when imaging the memory B with a low magnification, and the moving amount of the stage 106 and the beam current value are larger. That is, it indicates that the image should be taken in a more defocused state. In the memory hybrid logic E, the control condition is equal to the control condition of the memory B because the circuit pattern has a cell pitch of about 15 μm. The imaging conditions at the time of high-magnification imaging are all equal to “control condition 1” when the electron beam diameter on the sample is the smallest under the imaging conditions of “control condition 1”, that is, the electron beam image is This is because a condition for capturing a digital electron beam image at high resolution without blurring is meant.

FIG. 15 shows a generalized version of the table shown in FIG. That is, the imaging conditions of the electron beam image are set in the imaging magnification setting unit 202, as well as the type and position information of the target substrate (sample) in which the defect site is stored in the sample information and inspection information storage unit 201. The A / D converter 116 includes an imaging magnification (which basically includes a low magnification and a high magnification) and a sampling interval for converting an analog image signal into a digital image signal. On the other hand, control patterns for capturing an electron beam image include a moving distance of a stage, a numerical aperture of an objective lens, and a beam current for changing a focus state of irradiating an electron beam to a surface of a sample, and performing a filtering process. There are an analog filter and a digital filter. As described above, the correspondence between the imaging condition shown in FIG. 15A and the control pattern shown in FIG. 15B is stored in advance in the storage device in the overall control unit 210, the beam spot diameter control unit 203, or the signal processing control unit 702. If it is stored in a table (not shown) and prepared as a table, the overall control unit 210, the beam spot diameter control unit 203, or the signal processing control unit 702 can detect the defect of the target substrate (sample) to be put into the electron microscope. It is possible to select a control pattern according to an imaging condition suitable for a part.

FIG. 2 shows a scanning electron microscope 1 according to the present invention.
In the figure, a configuration is shown in which a network 201 and one or more visual inspection apparatuses 1203 are connected to a network 1204. The scanning electron microscope 1201 is provided with an inspection information receiving unit 1202, and can receive inspection information obtained from various appearance inspection devices 1203 via a network. The inspection information may be transmitted via another computer such as a production line management device 1205 for managing the production line connected on the network 1204, or may be directly transferred from the visual inspection device 1203. The inspection information is the appearance inspection device 1203
For example, it means the position of the detected defect in the target substrate and the defect size. The inspection information is input to the sample information and inspection information storage unit 201 in the scanning electron microscope 1201 via the general control unit 210 and stored. The sample information and inspection information storage unit 201 can also store information such as design values of circuit patterns formed on the target substrate, in addition to the inspection information.
Considering that the defects detected by the various visual inspection devices 1203 are to be observed in detail using the scanning electron microscope 1201, the defects to be observed usually include a plurality of defects in one target substrate. Capturing all images can be a great effort. According to the present invention, the maximum spatial frequency of a pattern in the vicinity (background) of each defective portion is obtained from the position of each defective portion and the design value of the circuit pattern formed on the target substrate, and the maximum spatial frequency is determined in accordance with the magnification at the time of imaging. Thus, the electron beam can be controlled to be in a defocused state so as not to generate pseudo noise, and a digital electron beam image can be captured by performing a filtering process. After the imaging of one defect, by operating to continuously image the other defects, even if there are many defective parts in one target substrate, without manual intervention,
It is possible to specify the positions of all the defective portions, obtain a high-resolution digital electron beam image of the specified defective portions, and perform a detailed analysis. In addition to the configuration shown in FIG.
The same applies to the case where not only 3 but also other inspection devices (for example, a tester that performs an operation test of each chip formed on the target substrate) and one or more observation devices including the microscope according to the present invention are connected. The effect of is obtained.

[0050]

According to the present invention, even when the sample to be imaged, the magnification to be imaged, and the cycle at the time of digital sampling are changed, it is possible to accurately image the sample without generating pseudo noise under each condition. Will be possible. Further, according to the present invention, even when an image of a target substrate is imaged at any magnification, the obtained digital image is automatically imaged accurately without generating pseudo noise, and a defect portion is detected. There is an effect that the characteristic amount or the property of the defective portion can be analyzed with respect to the defective portion by specifying the position.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a scanning electron microscope according to the present invention.

FIG. 2 is a diagram showing a schematic configuration of an entire system using a scanning electron microscope according to the present invention.

FIG. 3 is a diagram showing a processing flow of image acquisition using a scanning electron microscope according to the present invention.

FIG. 4 is a diagram showing a pattern formed on a sample according to the present invention and a foreign matter defect present on the sample, and a diagram showing an analog signal waveform of an electron beam detected by a focus state of an electron beam to be irradiated. It is.

FIG. 5 is a diagram illustrating a relationship between an imaging region using an electron beam and a two-dimensional digital image captured.

FIG. 6 is a diagram showing a beam spot diameter in a focus state of an electron beam to be switched and controlled on a sample (substrate to be processed).

FIG. 7 is a diagram showing a control flow for controlling an electron beam to be imaged on a sample (substrate to be processed) in a defocused state.

FIG. 8 is a schematic configuration diagram showing a second embodiment of the scanning electron microscope according to the present invention.

FIG. 9 is a schematic configuration diagram showing a third embodiment of the scanning electron microscope according to the present invention.

FIG. 10 is a schematic configuration diagram showing a fourth embodiment of the scanning electron microscope according to the present invention.

11 is a diagram illustrating an example of a specific configuration of the analog signal processing unit illustrated in FIG. 10;

FIG. 12 is a schematic configuration diagram showing a fifth embodiment of the scanning electron microscope according to the present invention.

13 is a diagram showing one embodiment of a specific configuration of the digital signal processing unit shown in FIG.

FIG. 14 is a diagram showing sample information and inspection information input to the overall control unit and stored in the sample information and inspection information storage unit, and control information including the imaging magnification set in the imaging magnification setting unit.

FIG. 15 is a diagram showing a table in which a correspondence between an imaging condition and a control pattern is stored in a storage device in the overall control unit, the beam spot diameter control unit, or the signal processing control unit in advance.

[Explanation of symbols]

101: electron gun, 102: electron beam, 103: converging lens, 104: deflection coil, 105: objective lens, 10
6 ... stage, 107 ... sample (substrate), 108 ...
Deflection control unit, 109 Objective lens control unit, 110 Stage drive control unit, 111 Secondary electron, 112 Secondary electron detector, 113 Analog electric signal, 114 Signal amplification unit, 115 Display device, 116 ... A / D conversion unit, 117
... frame memory, 118 ... D / A conversion unit, 119 ... image storage unit, 120 ... image processing unit, 201 ... sample information and inspection information storage unit, 202 ... imaging magnification setting unit, 203 ... beam spot diameter control unit, 204 ... Stage control signal, 2
06: objective lens control signal, 207: electron gun control signal,
210: overall control unit, 301: imaging area, 302: 2
Dimensional digital image, 404 ... beam spot diameter, 701
... Analog signal processing control signal, 702 ... Signal processing control section, 703 ... Analog signal processing section, 802 ... Frequency filter circuit, 803 ... Switch control section, 804 ... Switch circuit, 901 ... Digital signal processing unit, 903 ... Digital signal processing Control signal, 1001 program memory, 1002 program control unit, 1003 microprocessor, 1201 scanning electron microscope, 1202
Inspection information and sample information receiving unit, 1203 ... appearance inspection device, 1204 ... network, 1205 ... production line management system, 1206 ... CAD system.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Atsushi Shimoda 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Production Technology Research Institute (72) Inventor Kenji Ohara 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi, Ltd. Production Technology Research Laboratories (72) Inventor Yasuhiko Ozawa 882 Ma, Hitachinaka-shi, Ibaraki Pref.Hitachi, Ltd.Measurement Division, Hitachi Ltd. (72) Inventor Eika Baba 882 Ma, Hitachinaka-shi, Ibaraki Shares Within Hitachi Measuring Instruments Division (72) Inventor Shizushi Isogai 882 Ma, Hitachinaka-shi, Ibaraki Prefecture Within Hitachi Measuring Instruments Division (72) Inventor Kenji Watanabe 5--20, Josuihoncho, Kodaira-shi, Tokyo No. 1 Inside Semiconductor Business Division of Hitachi, Ltd. (72) Inventor Chie Shishido Totsuka, Yokohama-shi, Kanagawa Yoshida-cho 292 address Co., Ltd. Hitachi, Ltd., Institute of Industrial Science, the F-term (reference) 2G001 AA03 BA07 BA11 BA15 FA01 FA23 GA06 HA07 JA02 KA03 LA11 MA05 2G051 AA51 AB02 BA05 BA10 BA20 BC05 CB10 EA12 GC20

Claims (25)

[Claims] A stage on which a target substrate is placed; an electron gun for emitting an electron beam; a converging lens for converging the electron beam emitted from the electron gun; Scanning means for two-dimensionally scanning the surface of the target substrate, an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate, and scanning the electron beam by the scanning means. A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. A scanning electron microscope comprising: an A / D conversion unit that samples and converts the digital image signal into a digital image signal; A switching control unit that switches and controls at least the scanning unit so as to obtain a low-magnification digital image signal based on a narrow imaging field of view and a high-magnification digital image signal based on a narrow imaging field of view. A scanning electron microscope, comprising: a beam spot diameter control unit that switches and controls the spot diameter of the electron beam on the surface of the target substrate when performing the operation. 2. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and outputting an analog image signal detected and output from the detector. A scanning electron microscope comprising: an A / D conversion unit that samples and converts the digital image signal into a digital image signal; A switching control unit that switches and controls at least the scanning unit so as to obtain a low-magnification digital image signal based on a narrow imaging field of view and a high-magnification digital image signal based on a narrow imaging field of view. A beam spot diameter control unit that controls a spot diameter of an electron beam based on information on a surface state of an imaging portion of a target substrate when imaging is performed in a wide imaging field of view. . 3. The scanning electron microscope according to claim 1, wherein the beam spot diameter control unit is configured to control the movement of the stage in an electron beam irradiation direction. 4. The scanning electron microscope according to claim 1, wherein said beam spot diameter control section is configured by controlling said objective lens. 5. The scanning electron microscope according to claim 1, wherein the beam spot diameter control section is configured by controlling a current of an electron beam emitted from the electron gun. 6. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a convergent lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the convergent lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and outputting an analog image signal detected and output from the detector. A scanning electron microscope comprising: an A / D conversion unit that samples and converts the digital image signal into a digital image signal; A switching control unit that switches and controls at least the scanning unit so as to obtain a low-magnification digital image signal based on a narrow imaging field of view and a high-magnification digital image signal based on a narrow imaging field of view. And a control unit for controlling generation of a pseudo noise component from an imaging portion of the target substrate when imaging is performed in a wide imaging field of view. 7. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converging by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and outputting an analog image signal detected and output from the detector. A scanning electron microscope comprising: an A / D conversion unit that samples and converts the digital image signal into a digital image signal; A switching control unit that switches and controls at least the scanning unit so as to obtain a low-magnification digital image signal based on a narrow imaging field of view and a high-magnification digital image signal based on a narrow imaging field of view. When imaging is performed in a wide imaging field of view, a signal for reducing a high-frequency pseudo-noise component by performing signal processing on an analog image signal output from the detector in accordance with a surface state of an imaging portion of the target substrate. A scanning electron microscope comprising a processing unit. 8. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate, an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate, and scanning the electron beam by the scanning means. A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. A scanning electron microscope comprising: an A / D conversion unit that samples and converts the digital image signal into a digital image signal; A switching control unit that switches and controls at least the scanning unit so as to obtain a digital image signal based on a narrow imaging field of view and a digital image signal based on a narrow imaging field of view. A signal processing unit that performs signal processing on the digital image signal obtained from the A / D conversion unit in accordance with a surface state of an imaging part of the target substrate to reduce a high-frequency pseudo noise component. A scanning electron microscope, characterized in that: 9. The scanning electron microscope according to claim 7, wherein said signal processing section is configured to perform filtering signal processing. 10. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. A scanning electron microscope including an A / D converter for sampling and converting the digital image signal into a digital image signal, wherein an object to be mounted placed on the stage is provided. Based on the position coordinates of the defective part existing on the elephant substrate, the defective part is positioned in a wide imaging field of view, and the wide imaging field of view is obtained by defocusing the electron beam on the located defective part. And irradiates the analog image signal from the detector, and converts the detected analog image signal into the A / A signal.
A position conversion unit that converts the digital image signal into a low-magnification digital image signal in the D conversion unit, and specifies the position of the defect site based on the converted digital image signal indicating the low-magnification defect site; Positioning the defective portion in the narrow imaging field of view based on the position of the defective portion, and scanning and irradiating the located defective portion with an electron beam in a focused state so as to obtain the narrow imaging field of view, and performing the detection. An analog image signal is detected from the detector, and the detected analog image signal is converted into a high-magnification digital image signal by the A / D converter. And a analyzing means for analyzing a characteristic amount or a property of the defect portion. 11. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. A scanning electron microscope including an A / D converter for sampling and converting the digital image signal into a digital image signal, wherein an object to be mounted placed on the stage is provided. Based on the position coordinates of the defective part existing on the elephant substrate, the defective part is positioned in a wide imaging field of view, and control is performed on the positioned defective part so as to suppress generation of a pseudo noise component from the background. The electron beam is scanned and irradiated so as to obtain the wide imaging field of view, an analog image signal is detected from the detector, and the detected analog image signal is converted into a low-magnification digital image signal by the A / D converter. A position specifying means for specifying the position of the defective part based on the converted digital image signal indicating the defective part with a low magnification; and a defective part based on the position of the defective part specified by the position specifying means. It is positioned within a narrow imaging field of view, scans and irradiates the located defect site with an electron beam in a focused state so as to obtain the narrow imaging field of view, and the detector detects an analog beam. A / D converter converts the detected analog image signal into a high-magnification digital image signal, and detects a defect based on the converted digital image signal indicating the high-magnification defect portion. A scanning electron microscope, comprising: analysis means for analyzing a feature amount or a property of a part. 12. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. A scanning electron microscope including an A / D converter for sampling and converting the digital image signal into a digital image signal, wherein an object to be mounted placed on the stage is provided. Based on the position coordinates of the defective part present on the elephant substrate, the defective part is positioned in a wide imaging field of view, and the spot size is controlled based on the background information for the positioned defective part so that the electron beam is emitted. Scanning irradiation is performed so as to obtain a wide imaging field of view, an analog image signal is detected from the detector, and the detected analog image signal is converted into a low-magnification digital image signal by the A / D converter. Position specifying means for specifying the position of the defective part based on the digital image signal indicating the low-magnification defective part, and the defective part in a narrow imaging field of view based on the position of the defective part specified by the position specifying means. In the focused state, the electron beam is scanned and irradiated so as to obtain the narrow imaging visual field in a focused state, and an analog image signal is detected from the detector. The detected analog image signal is converted into a high-magnification digital image signal by the A / D converter, and the characteristic amount of the defect portion or its characteristic amount is determined based on the converted digital image signal indicating the high-magnification defect portion. A scanning electron microscope, comprising: analysis means for analyzing properties. 13. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. A scanning electron microscope including an A / D converter for sampling and converting the digital image signal into a digital image signal, wherein an object to be mounted placed on the stage is provided. Based on the position coordinates of the defective portion existing on the elephant substrate, the defective portion is positioned in a wide imaging field of view, and the located defective portion is scanned and irradiated with an electron beam so as to obtain the wide imaging field. Detecting an analog image signal from the detector, performing signal processing on the detected analog image signal in accordance with the background state of the defective portion to reduce a high-frequency pseudo-noise component due to the background, The analog image signal in which the pseudo noise component is reduced is converted into a low-magnification digital image signal by the A / D converter, and the position of the defect is determined based on the converted digital image signal indicating the low-magnification defect. Position specifying means for specifying, and positioning the defective part in a narrow imaging field of view based on the position of the defective part specified by the position specifying means, Is scanned and irradiated with an electron beam in a focused state so as to obtain a narrow imaging visual field, an analog image signal is detected from the detector, and the detected analog image signal is converted into a high-magnification image by the A / D converter. A scanning electron microscope comprising: a digital image signal; and analysis means for analyzing a characteristic amount or a property of the defective portion based on the converted digital image signal indicating the high-magnification defective portion. . 14. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converging by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. A scanning electron microscope including an A / D converter for sampling and converting the digital image signal into a digital image signal, wherein an object to be mounted placed on the stage is provided. Based on the position coordinates of the defective portion existing on the elephant substrate, the defective portion is positioned in a wide imaging field of view, and the located defective portion is scanned and irradiated with an electron beam so as to obtain the wide imaging field. Detecting an analog image signal from the detector, converting the detected analog image signal into a low-magnification digital image signal by the A / D converter, and converting the converted low-magnification digital image signal. Signal processing is performed in accordance with the background state of the defective portion to reduce high-frequency pseudo-noise components due to the background, and the high-frequency pseudo-noise component is reduced. Position specifying means for specifying the position of the defective part, and positioning the defective part in a narrow imaging field of view based on the position of the defective part specified by the position specifying means. The defective portion is scanned and irradiated with an electron beam in a focused state so as to obtain a narrow imaging visual field, an analog image signal is detected from the detector, and the detected analog image signal is processed by the A / D conversion section. Analyzing means for converting the digital image signal into a digital image signal of a magnification, and analyzing the characteristic amount or the property of the defective portion based on the converted digital image signal indicating the defective portion of the high magnification. electronic microscope. 15. A position of a defective portion is specified by extracting a difference image signal between a digital image signal indicating a low-magnification defective portion and a reference digital image signal having no low-magnification defective portion. The scanning electron microscope according to claim 10, wherein the scanning electron microscope is configured to perform the following. 16. The apparatus according to claim 10, wherein said position specifying means includes a display device for displaying a digital image signal indicating a defective portion with a low magnification.
Or a scanning electron microscope according to 13 or 14. 17. The apparatus according to claim 10, wherein said position specifying means is configured to acquire position coordinates of a defective portion existing on a target substrate mounted on a stage from a visual inspection apparatus. The scanning electron microscope according to 11 or 12 or 13 or 14. 18. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. Solution of a defective part existing on a target substrate by a scanning electron microscope equipped with an A / D converter for sampling and converting into a digital image signal In the method, the defect site is located in a wide imaging field of view based on the position coordinates of the defect site present on the target substrate placed on the stage, and an electron beam is directed to the located defect site. In the defocused state, scanning irradiation is performed so as to obtain the wide imaging field of view, an analog image signal is detected from the detector, and the detected analog image signal is converted into the A / A signal.
A D conversion unit for converting the digital image signal into a low-magnification digital image signal, a position specifying step for specifying the position of the defective part based on the converted digital image signal indicating the low-magnification defective part; Positioning the defective portion in the narrow imaging field of view based on the position of the defective portion, and scanning and irradiating the located defective portion with an electron beam in a focused state so as to obtain the narrow imaging field of view, and performing the detection. An analog image signal is detected from the detector, and the detected analog image signal is converted into a high-magnification digital image signal by the A / D converter. And analyzing the characteristic amount or the property of the defect part by using a scanning electron microscope. 19. A stage on which a target substrate is placed, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. Solution of a defective part existing on a target substrate by a scanning electron microscope having an A / D converter for sampling and converting into a digital image signal In the method, the defect site is located in a wide imaging field of view based on the position coordinates of the defect site present on the target substrate mounted on the stage, and the located defect site is simulated from the background. The electron beam is scanned and irradiated so as to obtain the wide imaging field of view by controlling so as to suppress generation of noise components, an analog image signal is detected from the detector, and the detected analog image signal is converted to the A / A signal. A D conversion unit for converting the digital image signal into a low-magnification digital image signal, a position specifying step for specifying the position of the defective part based on the converted digital image signal indicating the low-magnification defective part; Based on the position of the defective part, the defective part is positioned within the narrow imaging field of view, and the narrow imaging field of view is focused on the positioned defective part by focusing the electron beam. Scanning irradiation is performed so that an analog image signal is detected from the detector, and the detected analog image signal is converted into a high-magnification digital image signal by the A / D converter. And analyzing the characteristic amount or the property of the defective part based on the digital image signal indicating the defective part. 20. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a convergent lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the convergent lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. Solution of a defective part existing on a target substrate by a scanning electron microscope having an A / D converter for sampling and converting into a digital image signal In the method, the defect site is located in a wide imaging field of view based on the position coordinates of the defect site present on the target substrate mounted on the stage, and background information is provided for the located defect site. The electron beam is scanned and irradiated so as to obtain the wide imaging field of view by controlling the spot diameter based on the basis, an analog image signal is detected from the detector, and the detected analog image signal is converted by the A / D converter. Converting the digital image signal into a low-magnification digital image signal, and specifying a position of the defect site based on the converted digital image signal indicating the low-magnification defect site; Positioning the defective portion in the narrow imaging field of view based on the position, and scanning the located defective portion with the electron beam in a focused state so as to obtain the narrow imaging field of view. Irradiation, an analog image signal is detected from the detector, and the detected analog image signal is converted into a high-magnification digital image signal by the A / D converter, and indicates the converted high-magnification defect portion. An analysis step of analyzing a characteristic amount or a property of the defect portion based on the digital image signal. 21. A stage on which a target substrate is placed, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; and an analog image signal detected and output from the detector. Solution of a defective part existing on a target substrate by a scanning electron microscope equipped with an A / D converter for sampling and converting into a digital image signal In the method, the defect site is located in a wide imaging field of view based on the position coordinates of the defect site present on the target substrate placed on the stage, and an electron beam is directed to the located defect site. Scanning and irradiating so as to obtain the wide imaging field of view, detecting an analog image signal from the detector, performing signal processing on the detected analog image signal in accordance with the background state of the defective portion, and The high-frequency pseudo noise component is reduced, and the analog image signal in which the high-frequency pseudo noise component is reduced is converted into a low-magnification digital image signal by the A / D converter. A position specifying step of specifying the position of the defective part based on the digital image signal shown, and narrow imaging of the defective part based on the position of the defective part specified by the position specifying step It is positioned in the field of view, scans and irradiates the electron beam with respect to the located defective portion in a focused state so as to obtain a narrow imaging field of view, detects an analog image signal from the detector, and detects the detected analog image. An analysis process of converting the signal into a high-magnification digital image signal by the A / D converter, and analyzing the characteristic amount or the property of the defect site based on the converted digital image signal indicating the high-magnification defect site; A method for analyzing a defective portion by using a scanning electron microscope, comprising: 22. A stage on which a target substrate is mounted, an electron gun for emitting an electron beam, a converging lens for converging the electron beam emitted from the electron gun, and an electron beam converged by the converging lens. Scanning means for two-dimensionally scanning the surface of the target substrate; an objective lens for converging the electron beam converged by the converging lens into a spot on the surface of the target substrate; A detector for detecting an intensity of at least one of secondary electrons, reflected electrons, or absorbed electrons generated from the target substrate by scanning and outputting an analog image signal; Solution of a defective part existing on a target substrate by a scanning electron microscope equipped with an A / D converter for sampling and converting into a digital image signal In the method, the defect site is located in a wide imaging field of view based on the position coordinates of the defect site present on the target substrate placed on the stage, and an electron beam is directed to the located defect site. Scanning irradiation is performed so as to obtain the wide imaging field of view, an analog image signal is detected from the detector, and the detected analog image signal is converted into a low-magnification digital image signal by the A / D converter. The converted low-magnification digital image signal is subjected to signal processing according to the background state of the defective portion to reduce high-frequency pseudo-noise components due to the background. A position specifying step of specifying the position of the defective part based on the digital image signal indicating the defective part; and Positioned within a narrow imaging field of view, scans and irradiates the located defect site with an electron beam to obtain a narrow imaging field of view in a focused state, detects an analog image signal from the detector, and detects the detected An analog image signal is converted into a high-magnification digital image signal by the A / D converter, and the characteristic amount or the property of the defect is analyzed based on the converted digital image signal indicating the high-magnification defect. And a method for analyzing a defective part by a scanning electron microscope. 23. In the position specifying step, a position of a defective portion is specified by extracting a difference image signal between a digital image signal indicating a low-magnification defective portion and a reference digital image signal having no low-magnification defective portion. 23. The method according to claim 18, wherein
A method for analyzing a defective part by a scanning electron microscope according to the above. 24. The scanning electron microscope according to claim 18, wherein in the position specifying step, a digital image signal indicating a low magnification defect site is displayed on a display device. Defect site analysis method. 25. The method according to claim 18, wherein in the position specifying step, position coordinates of a defective portion existing on the target substrate placed on the stage are obtained from a visual inspection device. 23. The method for analyzing a defective portion by using a scanning electron microscope according to 21 or 22.