JP2021110556A - Pattern inspection device failure diagnosis method and pattern inspection device - Google Patents

Abstract

To provide a method for performing self-diagnosis on whether a failure with a possibility to miss a defect is occurring in an inspection device.SOLUTION: A pattern inspection device failure diagnosis method includes steps of: acquiring a first optical image of a predetermined area of a substrate with a pattern formed thereon by using an image acquisition mechanism S102; calculating first values of a plurality of pixels of the first optical image by using data of the first optical image S106; acquiring a second optical image of the predetermined area of a substrate which is the same as that of the area of the first optical image in the middle of a substrate pattern inspection S144; calculating second values of a plurality of pixels of the second optical image by performing calculation being the same as the calculation of the first values by using data of the second optical image S146; and determining a failure of the pattern inspection device in a case with presence of pixels where a difference between the first values of the plurality of pixels of the first optical image and the second values of the plurality of pixels of the second optical image is deviated from a range of a difference threshold, and then outputting a result S148.SELECTED DRAWING: Figure 3

Description

The present invention relates to a failure diagnosis method for a pattern inspection device and a pattern inspection device. For example, the present invention relates to an apparatus and a method for inspecting a pattern defect of an object used in semiconductor manufacturing.

In recent years, with the increasing integration and capacity of large-scale integrated circuits (LSIs), the circuit line width required for semiconductor devices has become narrower and narrower. Further, improvement of the yield is indispensable for manufacturing an LSI, which requires a large manufacturing cost. One of the major factors that reduce the yield is the pattern defect of the original plate that transfers the pattern. For example, there is a defect in a pattern that can be resolved by ultraviolet light. Further, with such miniaturization, development of a technique for transferring an unresolution pattern having a size that is difficult to resolve with an inspection device using ultraviolet light, for example, several nm to several tens of nm, is being promoted. For example, the development of nanoimprint lithography technology for transferring a pattern by pressing a template on which a fine uneven pattern is formed against a sample is underway. Therefore, as the pattern defect of the original plate, in addition to the defect of the pattern that can be resolved, for example, the defect of the pattern that is difficult to resolve with ultraviolet light can be mentioned.

Therefore, it is necessary to improve the accuracy of the pattern inspection apparatus for inspecting the pattern defects of the original plate. As an inspection method, for example, a "die to die inspection" method for comparing optical images of the same pattern in different places on the same original plate has been proposed (see, for example, Patent Document 1). ..

In the inspection device, an image of a region containing a defect is sampled before inspection, and an inspection threshold value is set so that the defect can be detected. However, even if a defect can be detected before the inspection, if a failure occurs in the optical system of the device during the inspection, a situation may occur in which what should be detected as a defect is missed. Can be done. Therefore, there is a need for a function of self-diagnosing whether or not a failure that may cause a defect to be missed has occurred.

Japanese Unexamined Patent Publication No. 2016-206169

Therefore, one aspect of the present invention provides an inspection device equipped with a method capable of self-diagnosing whether or not a failure in which a defect may be missed has occurred in the inspection device and a function for executing such a method.

The method for diagnosing a failure of the pattern inspection device according to one aspect of the present invention is as follows.
A step of acquiring a first optical image of a predetermined region of the substrate before starting the pattern inspection of the substrate on which the pattern is formed by using the image acquisition mechanism of the pattern inspection apparatus.
A step of calculating the first value of a plurality of pixels of the first optical image using the acquired data of the first optical image in a predetermined region, and
A step of acquiring a second optical image of the above-mentioned predetermined region of the same substrate as the region of the first optical image during the pattern inspection of the substrate by using the image acquisition mechanism.
A step of calculating the second value of a plurality of pixels of the second optical image by performing the same calculation as the calculation of the first value using the acquired data of the second optical image in the predetermined region. ,
When there is a pixel in which the difference between the first value of the plurality of pixels of the first optical image and the second value of the plurality of pixels of the second optical image is out of the range of the difference threshold, the pattern inspection apparatus The process of determining a failure and outputting the result,
It is characterized by being equipped with.

Further, as a predetermined region, it is preferable to use a region including a defective portion in the region where a pattern is formed on the substrate.

Alternatively, it is preferable that any region of the regions on which the pattern is formed on the substrate is used as the predetermined region.

In addition, the inspection area of the substrate is divided into a plurality of stripe areas.
Pattern inspection is performed for each stripe area of multiple stripe areas,
It is preferable that a second optical image of a predetermined region is acquired after the number of stripe regions in which defects of the pattern formed on the substrate are no longer detected reaches a predetermined number.

The pattern inspection device of one aspect of the present invention is
The first optical image of a predetermined region of the substrate is acquired before the pattern inspection of the substrate on which the pattern is formed is started, and the above-described substrate of the same substrate as the region of the first optical image is acquired during the pattern inspection of the substrate. An image acquisition mechanism for acquiring a second optical image of a predetermined region,
Using the acquired data of the first optical image of the predetermined region, the first values of the plurality of pixels of the first optical image are calculated, and the data of the second optical image of the acquired predetermined region is calculated. A calculation processing circuit that calculates the second value of a plurality of pixels of the second optical image by performing the same calculation as the calculation of the first value using
When there is a pixel in which the difference between the first value of the plurality of pixels of the first optical image and the second value of the plurality of pixels of the second optical image is out of the range of the difference threshold value, the pattern inspection device is used. Judgment processing circuit that determines failure and
It is characterized by being equipped with.

According to one aspect of the present invention, it is possible to self-diagnose whether or not a failure that may cause a defect to be missed has occurred in the inspection device.

It is a block diagram which shows the structure of the pattern inspection apparatus in Embodiment 1. FIG. It is a conceptual diagram for demonstrating the inspection area in Embodiment 1. FIG. It is a flowchart which shows an example of the main part process of the inspection method in Embodiment 1. FIG. It is a figure which shows an example of the internal structure of the diagnostic circuit in Embodiment 1. FIG. It is a figure for demonstrating the sampling area in Embodiment 1. FIG. It is a figure which shows an example of the internal structure of the comparison circuit in Embodiment 1. FIG. It is a figure for demonstrating an example of the reaction value of each pixel in Embodiment 1. FIG. It is a figure for demonstrating image acquisition for diagnosis in Embodiment 1. FIG. It is a figure for demonstrating the modification of Embodiment 1.

Embodiment 1.
FIG. 1 is a configuration diagram showing a configuration of a pattern inspection device according to the first embodiment. In FIG. 1, the inspection device 100 for inspecting defects in a pattern formed on a substrate to be inspected includes an optical image acquisition mechanism 150 and a control system circuit 160.

The optical image acquisition mechanism 150 includes a light source 103, an illumination optical system 170, a beam splitter 174, a magnifying optical system 104, a movablely arranged XYθ table 102, an imaging optical system 176, and a photodiode array 105 (an example of a sensor). It has a sensor circuit 106, a stripe pattern memory 123, and a laser length measuring system 122. A substrate 101 as a sample to be inspected is arranged on the XYθ table 102. The substrate 101 includes, for example, an exposure mask and a template for nanoimprint lithography. Further, in this template, an unresolved pattern that cannot be resolved at the wavelength of the light generated from the light source 103 is formed. Hereinafter, a case where, for example, a template in which an unresolution pattern is formed is used as the substrate 101 will be described. The substrate 101 is arranged on the XYθ table 102, for example, with the pattern forming surface facing downward.

In the control system circuit 160, the control computer 110 that controls the entire inspection device 100 uses the position circuit 107, the comparison circuit 108, the reference image creation circuit 112, the autoloader control circuit 113, the table control circuit 114, and the diagnostic circuit via the bus 120. It is connected to 140, a magnetic disk device 109, a GUI (graphic user interface) 116, an external interface (I / F) 117, a pattern monitor 118, and a printer 119. Further, the sensor circuit 106 is connected to the stripe pattern memory 123, and the stripe pattern memory 123 is connected to the comparison circuit 108. Further, the XYθ table 102 is driven by an X-axis motor, a Y-axis motor, and a θ-axis motor. The XYθ table 102 is an example of a stage.

A series of "~ circuits" such as a position circuit 107, a comparison circuit 108, a reference image creation circuit 112, an autoloader control circuit 113, a table control circuit 114, and a diagnostic circuit 140 have a processing circuit. Such processing circuits include electric circuits, computers, processors, circuit boards, quantum circuits, semiconductor devices, and the like. Further, a common processing circuit (same processing circuit) may be used for each “~ circuit”. Alternatively, different processing circuits (separate processing circuits) may be used. For example, a series of "~ circuits" such as a position circuit 107, a comparison circuit 108, a reference image creation circuit 112, an autoloader control circuit 113, a table control circuit 114, and a diagnostic circuit 140 may be configured and executed by the control computer 110. good. The program for executing the processor or the like may be recorded on a recording medium such as a magnetic disk device 109 or a ROM (read-only memory).

In the inspection device 100, a high-magnification inspection optical system is composed of a light source 103, an illumination optical system 170, a beam splitter 174, a magnifying optical system 104, an imaging optical system 176, a photodiode array 105, and a sensor circuit 106. Further, the XYθ table 102 is driven by the table control circuit 114 under the control of the control computer 110. It can be moved by a drive system such as a three-axis (XY-θ) motor that drives in the X, Y, and θ directions. As these X motors, Y motors, and θ motors, for example, step motors can be used. The XYθ table 102 can be moved in the horizontal direction and the rotational direction by the motor of each axis of the XYθ. Then, the moving position of the substrate 101 arranged on the XYθ table 102 is measured by the laser length measuring system 122 and supplied to the position circuit 107.

Here, FIG. 1 describes the components necessary for explaining the first embodiment. It goes without saying that the inspection apparatus 100 may usually include other necessary configurations.

FIG. 2 is a conceptual diagram for explaining an inspection area according to the first embodiment. As shown in FIG. 2, the inspection area 10 (entire inspection area) of the substrate 101 is virtually divided into a plurality of strip-shaped inspection stripes 20 (stripe areas) having a scan width W, for example, in the Y direction. .. The pattern inspection in the first embodiment is performed for each inspection stripe 20. In the pattern inspection, acquisition of an image used for inspection and comparison processing using the acquired image are performed. Therefore, the inspection device 100 acquires an image (stripe region image) for each inspection stripe 20. For each of the inspection stripes 20, a laser beam is used to capture an image of a graphic pattern arranged in the stripe region in the longitudinal direction (X direction) of the stripe region. By moving the XYθ table 102, the photodiode array 105 moves relatively continuously in the X direction, and an optical image is acquired. The photodiode array 105 continuously captures an optical image having a scan width W as shown in FIG. In other words, the photodiode array 105, which is an example of the sensor, captures an optical image of a pattern formed on the substrate 101 using inspection light while moving relative to the XYθ table 102 (stage). In the first embodiment, after the optical image of one inspection stripe 20 is captured, the optical image of the scan width W is similarly moved in the Y direction to the position of the next inspection stripe 20 and this time in the opposite direction. Images are taken continuously. That is, the imaging is repeated in the forward (FWD) -back forward (BWD) directions in the opposite directions on the outward and return paths.

Further, as shown in FIG. 2, the stripe region image of each inspection stripe 20 is divided into a plurality of frame images in the longitudinal direction by, for example, the scan width. Then, the inspection is performed for each frame image. The area in which the stripe area of each inspection stripe 20 is divided into the size of the frame image is the frame area 30. In other words, as shown in FIG. 2, the stripe region of each inspection stripe 20 is divided into a plurality of frame regions 30 in the longitudinal direction by, for example, the scan width. For example, it is divided into 512 × 512 pixel sizes. In the example of FIG. 2, the case where the size of each side of the frame area 30 and the width (short direction) size of the inspection stripe 20 are the same is shown, but the present invention is not limited to this. It can be of a different size. For example, it is preferable to set the size of each side of the frame area 30 to be 1/2 of the width (short direction) size of the inspection stripe 20.

Here, the direction of imaging is not limited to the repetition of forward (FWD) -back forward (BWD). Imaging may be performed from one direction. For example, FWD-FWD may be repeated. Alternatively, BWD-BWD may be repeated. Next, the image acquisition operation by the optical image acquisition mechanism 150 will be specifically described.

In the inspection region of the substrate 101, a laser beam (for example, DUV light) having a wavelength lower than the ultraviolet region, which is the inspection light, is applied to the beam splitter 174 by the illumination optical system 170 from an appropriate light source 103. The irradiated laser beam is reflected by the beam splitter 174 and is irradiated on the substrate 101 by the magnifying optical system 104. The light reflected from the substrate 101 passes through the magnifying optical system 104 and the beam splitter 174, is imaged as an optical image on the photodiode array 105 (an example of a sensor) by the imaging optical system 176, and is incident on the photodiode array 105. As the photodiode array 105, for example, it is preferable to use a TDI (time delay integration) sensor.

The image of the pattern formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105, and further A / D (analog-digital) converted by the sensor circuit 106. Then, the pixel data of the inspection stripe 20 to be measured is stored in the stripe pattern memory 123. After that, the stripe region image is sent to the comparison circuit 108 together with the data indicating the position of the substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) is, for example, 8-bit unsigned data, and represents the gradation (light intensity) of the brightness of each pixel.

Here, as described above, the template as an example of the substrate 101 may form an unresolution pattern that cannot be resolved at the wavelength of the light generated from the light source 103. In such a case, it is difficult to identify the shape of the formed graphic pattern from the obtained image. Further, in the frame region 30 which is the unit to be inspected, the same pattern is often repeatedly formed. Therefore, it is assumed that the gradation value of each pixel in the obtained image will be a close intermediate gradation value within a certain range if there is no defect. Therefore, in the first embodiment, for each pixel in the obtained image, the difference from the gradation value of another pixel in the same image is obtained as a reaction value, and the reaction value is compared with the reaction threshold value. An example will be described in which an inspection method for detecting a defect location is used. Since the inspection method does not perform comparison with the reference image created from the design data (die database inspection), the reference image creation circuit 112 of FIG. 1 may be omitted.

FIG. 3 is a flowchart showing an example of a main step of the inspection method according to the first embodiment. In FIG. 3, the inspection methods according to the first embodiment are a sampling area image (1) acquisition step (S102), an image (1) reaction value calculation step (S106), and a defect undetected stripe number threshold setting step (S112). , Inspection processing step (S120), determination step (S130), determination step (S140), moving step to sampling region (S142), sampling region image (2) acquisition step (S144), and image ( 2) A series of steps of a reaction value calculation step (S146) and a determination step (S148) are carried out. Further, the inspection processing step (S120) is referred to as a stripe image acquisition step (S122), a frame image creation step (S124), a reaction value calculation step (S126), and a comparison processing step (S128) as internal steps. Carry out a series of steps.

Sampling region image (1) As an acquisition step (S102), the optical image acquisition mechanism 150 (image acquisition mechanism) performs a sampling region (predetermined region) of the substrate 101 before starting the pattern inspection of the substrate 101 on which the pattern is formed. (First optical image) is acquired.

FIG. 4 is a diagram showing an example of the internal configuration of the diagnostic circuit according to the first embodiment. In FIG. 4, a storage device 80 such as a magnetic disk device, a sampling area setting unit 72, a defect undetected stripe number threshold setting unit 82, a determination unit 84, an image reacquisition control unit 86, and a determination unit are included in the diagnostic circuit 140. 88 is placed. A series of "~ units" such as a sampling area setting unit 72, a defect undetected stripe number threshold setting unit 82, a determination unit 84, an image reacquisition control unit 86, and a determination unit 88 have a processing circuit. Such processing circuits include electric circuits, computers, processors, circuit boards, quantum circuits, semiconductor devices, and the like. Further, a common processing circuit (same processing circuit) may be used for each “~ circuit”. Alternatively, different processing circuits (separate processing circuits) may be used. Input data or calculated results required for the sampling area setting unit 72, the defect undetected stripe number threshold setting unit 82, the determination unit 84, the image reacquisition control unit 86, and the determination unit 88 are stored in a memory (not shown) each time. NS.

First, the sampling area setting unit 72 sets a sampling area from the inspection area 10 of the substrate 101.

FIG. 5 is a diagram for explaining a sampling region in the first embodiment. As shown in FIG. 5, the sampling area setting unit 72 sets as the sampling area 11 a region including a defect portion 12 in the inspection region 10 on which the pattern is formed on the substrate 101. Here, the case where the region including the defect portion 12 which is supposed to show a characteristic reaction value is used is shown. However, it is not limited to this. Since it is sufficient to determine whether or not the same image is obtained before and during the inspection, the sampling area setting unit 72 can use any of the inspection areas 10 in which the pattern on the substrate 101 is formed as the sampling area 11. You may set the area. In such a case, since it is an arbitrary region, it is unknown whether or not there is a defect. It is preferable that the sampling region 11 is set to, for example, the same size as the frame region 30. However, it is not limited to this. The size may be smaller than the frame area 30. For example, the size may be set to 1/1 of n (n is an integer of 2 or more) of the frame area 30. Alternatively, the size may be larger than the frame area 30.

Then, the XYθ table 102 is moved to a position where the sampling area 11 can be imaged. Then, the optical image acquisition mechanism 150 acquires an optical image (sampling region image (1)) of the sampling region 11. The operation of acquiring the optical image is as described above. By moving the XYθ table 102, the photodiode array 105 moves relatively continuously in the X direction, and an optical image of the sampling region 11 is acquired. The image of the pattern formed on the photodiode array 105 is photoelectrically converted by each light receiving element of the photodiode array 105, and further A / D converted by the sensor circuit 106. Then, the pixel data of the sampling area 11 is stored in the stripe pattern memory 123. Here, the image may be taken in units of 20 inspection stripes including the sampling area 11, or only the sampling area 11 may be imaged. The captured optical image data of the sampling region 11 is sent to the comparison circuit 108 together with the data indicating the position of the substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) is, for example, 8-bit unsigned data, and represents the gradation (light intensity) of the brightness of each pixel.

FIG. 6 is a diagram showing an example of the internal configuration of the comparison circuit according to the first embodiment. In FIG. 6, storage devices 50, 54, 68 such as a magnetic disk device, a frame image creation unit 52, a reaction value calculation unit 56, and a comparison processing unit 58 are arranged in the comparison circuit 108. A series of "~ units" such as the frame image creation unit 52, the reaction value calculation unit 56, and the comparison processing unit 58 have a processing circuit. Such processing circuits include electric circuits, computers, processors, circuit boards, quantum circuits, semiconductor devices, and the like. Further, a common processing circuit (same processing circuit) may be used for each “~ circuit”. Alternatively, different processing circuits (separate processing circuits) may be used. The input data or the calculation result required for the frame image creation unit 52, the reaction value calculation unit 56, and the comparison processing unit 58 are stored in a memory (not shown) each time.

The captured optical image data of the sampling region 11 is stored in the storage device 50 in the comparison circuit 108. When the optical image data is captured in units of 20 inspection stripes including the sampling area 11, the frame image creation unit 52 creates a frame image of the sampling area 11. The frame image of the sampling area 11 is stored in the storage device 54. When the optical image data of the sampling area 11 is captured in the frame area 30 size or a size smaller than the frame area 30, it is stored in the storage device 54 without being processed by the frame image creating unit 52.

Image (1) As a reaction value calculation step (S106), the reaction value calculation unit 56 (calculation processing circuit) uses the acquired optical image data of the sampling area 11 to obtain a plurality of pixels of the optical image of the sampling area 11. The reaction value t1 (first value) is calculated.

FIG. 7 is a diagram for explaining an example of the reaction value of each pixel in the first embodiment. In the example of FIG. 7, the reaction value calculation unit 56 calculates, for example, the average value of the gradation values of all the pixels in the measurement image of the sampling area 11. Then, for each pixel in the measurement image of the sampling area 11, the difference between the gradation value of the target pixel 32 and the calculated average value is calculated as the reaction value t1. In the example of FIG. 7, the average value of the gradation values of all the pixels of the measurement image in the frame area 30 which is the sampling area 11 is, for example, 100, and the gradation value of the target pixel 32 is For example, if it is 120, the reaction value of the pixel 32 is 20. However, it is not limited to this. For example, a difference value between the average value of the gradation values of a plurality of pixels in the partial region 31 including the target pixel 32 and the gradation value of the target pixel 32 in the same image is also preferable. Alternatively, a difference value between the average value of the gradation values of a plurality of pixels of the pixel row 33 in the x-direction or the y-direction including the target pixel 32 and the gradation value of the target pixel 32 in the same image is also preferable. .. Alternatively, other statistical values (for example, median value, minimum value, etc.) may be used instead of these average values. Alternatively, the reaction value may be a ratio of the gradation value of the target pixel 32 to, for example, the average value, instead of the above-mentioned difference value. Alternatively, it may be a value calculated by another algorithm using the target pixel 32 and the gradation values of other pixels other than the target pixel 32. The calculated reaction value of each pixel is output to the diagnostic circuit 140 and stored in the storage device 80.

As described above, even if a defect can be detected before the inspection processing step (S120) (board pattern inspection), during the inspection, for example, an abnormality in the amount of light or a running abnormality in the XYθ table 102 may occur. , A situation in which the accuracy of the obtained image deteriorates and what should be detected as a defect is missed when a device failure such as a failure of the optical system or the traveling system used for acquiring the image occurs. Can occur. Therefore, there is a need for a function of self-diagnosing whether or not a failure that may cause a defect to be missed has occurred. Therefore, in the first embodiment, when the number of inspection stripes 20 in which defects have not been detected reaches a predetermined number as a result of inspection, it is determined whether or not a device failure such as a failure of an optical system or a traveling system has occurred. Diagnosis is made by the diagnostic circuit 140. To this end, first, a threshold is set for the number of inspection stripes 20 in which defects have not been detected for initiating failure diagnosis.

As the defect undetected stripe number threshold setting step (S112), the defect undetected stripe number threshold setting unit 82 sets the defect undetected stripe number threshold m for starting the failure diagnosis. As the defect-undetected stripe number threshold m, for example, a value of about 10 to 100 is preferable.

After each step before the above inspection process is executed, the inspection process step (S120) is carried out. In other words, an optical image of the sampling region 11 is acquired before the inspection for the presence or absence of defects in the pattern formed on the substrate 101 is started. In the inspection processing step (S120), the optical image acquired from the substrate 101 for each inspection stripe 20 is used to perform the same calculation as the calculation of the reaction values t1 of the plurality of pixels in the optical image of the sampling region 11 described above. By comparing the obtained reaction value (value to be inspected) with the preset determination threshold value th, the presence or absence of a defect in the pattern is inspected. Specifically, it operates as follows.

As a stripe image acquisition step (S122), the optical image acquisition mechanism 150 acquires an optical image from the substrate 101 for each inspection stripe 20. The method of acquiring the optical image is as described above. The acquired stripe region image data (stripe data) is sent to the comparison circuit 108 together with the data indicating the position of the substrate 101 on the XYθ table 102 output from the position circuit 107.

The stripe data (optical image data) input to the comparison circuit 108 is stored in the storage device 50. Further, the reaction threshold value th input to the comparison circuit 108 is stored in the storage device 66.

As a frame image creation step (S124), the frame image creation unit 52 creates a frame image for each frame region 30 from the stripe region image. For example, a frame image of 512 × 512 pixels is created. It is preferable that the plurality of frame images 30 are created so that the adjacent frame images 30 overlap each other with a predetermined margin width. By such processing, a plurality of frame images 30 (optical images) corresponding to the plurality of frame areas 30 are acquired. The plurality of frame images 30 are stored in the storage device 54. As a result, image (measured image) data to be compared for inspection is generated.

In the reaction value calculation step (S126), the reaction value calculation unit 56 calculates the reaction value t of a plurality of pixels for each frame image using the data of the frame image. The reaction value t calculated here is obtained by performing the same calculation as the calculation of the reaction values t1 of a plurality of pixels in the optical image of the sampling region 11. For example, for each pixel in the same frame image, the difference between the gradation value of the target pixel and the average value of the gradation values of all the pixels in the same frame image is calculated as the reaction value t.

As the comparison processing step (S128), the comparison processing unit 58 compares the reaction value t with the reaction threshold value th for each pixel and inspects the defect of the pattern in the frame image. For example, when the reaction value t is larger than the reaction threshold value th, it is determined as a defect. Then, the comparison result (inspection result) is output. The comparison result is stored in the storage device 68 and output to the magnetic disk device 109 and / and the pattern monitor 118, or / and is output to the outside via the external I / F 117. Alternatively / and may be output from the printer 119.

As a determination step (S130), the control computer 110 determines whether or not the inspection of all the inspection stripes 20 has been completed. If the inspection stripe 20 that has not been inspected remains, the process returns to the inspection processing step (S120), and the next inspection stripe 20 that has not been inspected is inspected. When the inspection of all the inspection stripes 20 is completed, the inspection process is terminated.

While the inspection process of the plurality of inspection stripes 20 is performed, the diagnostic circuit 140 performs the following operations.

In the determination step (S140), the determination unit 84 refers to the inspection results stored in the storage device 68 while the inspection processing of the plurality of inspection stripes 20 is performed, and determines the number of inspection stripes 20 in which defects have not been detected. For example, it is determined whether or not the defect-undetected stripe number threshold value m has been continuously reached. If the defect continues to be undetected, it is determined that there is a possibility that a device failure or the like has occurred when acquiring the image. If the defect-undetected stripe number threshold value m has not been reached, the inspection processing step (S120) is continued. When the defect-undetected stripe number threshold value m is reached, the process proceeds to the moving step to the sampling region (S142).

As a moving step (S142) to the sampling region, the table control circuit 114 moves the XYθ table 102 to a position where the sampling region 11 can be imaged under the control of the image reacquisition control unit 86.

FIG. 8 is a diagram for explaining image acquisition for diagnosis in the first embodiment. As shown in FIG. 9, if there is an inspection stripe 20 that has been imaged when it is determined that the number of undetected stripes threshold m has been reached, the inspection stripe 20 is at the time when the scanning operation is completed and before the inspection. It is preferable to return to the sampling region 11 imaged in order to set the reaction threshold value th. If it is determined to be normal as a result of the failure diagnosis and the image is returned to the sampling area 11 in the middle of the inspection stripe 20 that has been imaged, the scanning operation of the inspection stripe 20 that has been imaged will be redone. Therefore, by returning to the sampling area 11 when the scanning operation of the inspection stripe 20 that has been imaged is completed, it is possible to avoid re-scanning.

As a sampling region image (2) acquisition step (S144), the optical image acquisition mechanism 150 performs an optical image (Sampling region 11) of the sampling region 11 in the middle of a series of inspection processing steps (S120) (pattern inspection processing) before the start of inspection. The optical image (second optical image) of the sampling region 11 of the substrate 101, which is the same as the region of the first optical image), is acquired. In other words, under the control of the image reacquisition control unit 86, the optical image acquisition mechanism 150 again acquires the optical image (second optical image) of the sampling region 11 of the substrate 101 on which the pattern is formed. The optical image (second optical image) of the sampling region 11 is obtained after the number of inspection stripes 20 in which the defect of the pattern formed on the substrate 101 is no longer detected after the start of the pattern inspection process reaches a predetermined number. Then, the optical image (second optical image) of the sampling region 11 is acquired. The operation of acquiring the optical image is as described above. Here, the image may be taken in units of 20 inspection stripes including the sampling area 11, or only the sampling area 11 may be imaged. The captured optical image data of the sampling region 11 is sent to the comparison circuit 108 together with the data indicating the position of the substrate 101 on the XYθ table 102 output from the position circuit 107. The measurement data (pixel data) is, for example, 8-bit unsigned data, and represents the gradation (light intensity) of the brightness of each pixel.

The captured optical image (second optical image) data of the sampling region 11 is stored in the storage device 50. When the optical image data is captured in units of 20 inspection stripes including the sampling area 11, the frame image creation unit 52 creates a frame image of the sampling area 11. The frame image of the sampling area 11 is stored in the storage device 54. When the optical image data in the sampling area 11 is captured in the frame area 30 size or a size smaller than the frame area 30, it is stored in the storage device 54 without being processed by the frame image creating unit 52.

Image (2) As a reaction value calculation step (S146), the reaction value calculation unit 56 uses the data of the acquired optical image (second optical image) of the sampling region 11 to image (1) the reaction value calculation step. By performing the same calculation as the calculation of the reaction value t1 (first value) calculated in (S106), the reaction value t2 (second value) of a plurality of pixels of the optical image in the sampling region 11 is calculated.

If a failure of the optical system or the like occurs during the inspection process, it is assumed that the calculated reaction value becomes an abnormal value. When no equipment failure has occurred, the image acquired before the inspection (1) The reaction value t1 of the plurality of pixels calculated in the reaction value calculation step (S106) and the image acquired in the same sampling area 11 after the inspection is started. The difference between the image (2) and the reaction value t2 of the plurality of pixels calculated in the reaction value calculation step (S146) should remain within the error range. Therefore, the following determination process is performed.

As a determination step (S148), the determination unit 88 (determination processing circuit) uses the reaction values t1 of a plurality of pixels of the optical image of the sampling region 11 acquired before the inspection and the image (2) reaction value calculation step (S146). It is determined whether or not there is a pixel whose difference from the calculated reaction value t2 of the plurality of pixels is out of the range of the difference threshold value th'. The difference threshold th'may be set in advance. Specifically, for each pixel, it is determined whether or not the absolute value of the difference between the reaction value t1 and the reaction value t2 is larger than the difference threshold value th'. Then, the determination unit 88 determines that the inspection device 100 has failed when there is a pixel in which the difference between the reaction value t1 of the plurality of pixels and the reaction value t2 of the same plurality of pixels is out of the range of the difference threshold value th'. do. The determination result is output to the control computer 110. When there is no pixel in which the difference between the reaction value t1 of the plurality of pixels and the reaction value t2 of the same plurality of pixels is out of the range of the difference threshold value th', the control computer 110 determines the inspection stripe 20 in which the scanning operation is completed. The scanning operation of the stripe image is started from the next inspection stripe 20, and the inspection process is continued.

When there is a pixel in which the difference between the reaction value t1 of the plurality of pixels and the reaction value t2 of the same plurality of pixels is out of the range of the difference threshold value th', the control computer 110 diagnoses the device as a failure and inspects the device. Abnormally stop 100. As a result, it is possible to prevent the defect from being missed, which is supposed to be detected as a defect. After improving the equipment failure, the inspection may be performed again.

As described above, according to the first embodiment, it is possible to self-diagnose whether or not a failure that may cause a defect to be missed has occurred in the inspection device.

Here, in the above-described example, for each pixel in the self-image, the difference from the gradation value of another pixel in the same image is obtained as the reaction value, and the reaction value is compared with the reaction threshold value th. The case where an inspection method for detecting a defect location is used has been described, but the inspection method is not limited to this. For example, a die-die inspection may be performed.

FIG. 9 is a diagram for explaining a modification of the first embodiment. In the die-die inspection, optical images obtained by capturing the same pattern at different locations on the same substrate 101 are compared with each other. Therefore, the optical image of the sampling region 11a of the die (1) and the optical image of the sampling region 11b of the die (2) on which the same pattern is formed are acquired. Then, for each pixel, a value calculated by a predetermined algorithm using the gradation value of the pixel of the image of the die (1) and the gradation value of the pixel of the image of the die (2) is calculated as the reaction value t1. .. For example, it is preferable to set the reaction value t1 to the difference between the gradation value of the pixel of the image of the die (1) and the gradation value of the pixel of the image of the die (2) for each pixel. Similarly, in the inspection processing step (S120), the difference between the gradation value of the pixel of the frame image of the die (1) and the gradation value of the pixel of the frame image of the corresponding die (2) is used as the reaction value t. It is also preferable to calculate and compare with the reaction threshold value th. In the failure diagnosis, the optical image of the sampling region 11a of the die (1) and the optical image of the sampling region 11b of the die (2) on which the same pattern is formed are acquired again, and the reaction value t2 is calculated for each pixel. do it. Other contents may be the same as the above-mentioned contents.

In addition, as an inspection method, for example, a die database inspection may be carried out. In the die database inspection, the image obtained from the substrate 101 is compared with the reference image calculated from the design pattern data that is the basis of the pattern formed on the substrate 101. Therefore, an optical image of the sampling region 11 of the substrate 101 is acquired, and a reference image of the same region is created. Then, for each pixel, a value calculated by a predetermined algorithm using the gradation value of the pixel of the optical image and the gradation value of the pixel of the reference image is calculated as the reaction value t1. Similarly, in the inspection processing step (S120), the value calculated by a predetermined algorithm using the gradation value of the pixel of the frame image acquired from the substrate 101 and the gradation value of the pixel of the corresponding reference image is calculated. It is also preferable to calculate it as the reaction value t and compare it with the reaction threshold th. In the failure diagnosis, the optical image of the sampling region 11 may be acquired again, and the reaction value t2 may be calculated for each pixel with the reference image. Other contents may be the same as the above-mentioned contents.

The reference image is created by the reference image creation circuit 112. The reference image creation circuit 112 reads drawing data (design pattern data) from the storage device 109 through the control computer 110, and converts each graphic pattern defined in the read design pattern data into binary or multi-valued image data. do.

The figure defined in the design pattern data is, for example, a basic figure of a rectangle or a triangle. For example, the coordinates (x, y) at the reference position of the figure, the length of the side, and the figure type such as the rectangle or the triangle are distinguished. Graphical data that defines the shape, size, position, etc. of each pattern graphic is stored with information such as a graphic code that serves as an identifier.

When the design pattern data to be the graphic data is input to the reference image creation circuit 112, it is expanded to the data for each graphic, and the graphic code, the graphic dimension, etc. indicating the graphic shape of the graphic data are interpreted. Then, it is developed into binary or multi-valued design pattern image data as a pattern arranged in a grid having a grid of predetermined quantization dimensions as a unit and output. In other words, the design data is read, the occupancy rate of the figure in the design pattern is calculated for each square created by virtually dividing the frame area 30 into squares having a predetermined dimension as a unit, and the occupancy rate data of n bits is calculated. (Design image data) is output. For example, it is preferable to set one square as one pixel. Then, when to have a resolution of 1/2 8 ^{(= 1/256)} to 1 pixel, the occupancy rate of the pixel allocated the small area region amount corresponding 1/256 of figures are arranged in a pixel Calculate. Then, it is created as 8-bit occupancy rate data. Such squares (inspection pixels) may be matched with the pixels of the measurement data. Further, a reference image is created by performing a predetermined filter process on the obtained design image according to the optical characteristics. The created reference image may be output to the comparison circuit 108.

The embodiment has been described above with reference to a specific example. However, the present invention is not limited to these specific examples. For example, in the embodiment, the reflected illumination optical system using reflected light is shown as the illumination optical system 170, but the present invention is not limited to this. For example, it may be a transmitted illumination optical system using transmitted light. Alternatively, the transmitted illumination optical system and the reflected illumination optical system may be combined to use the transmitted light and the reflected light at the same time.

Further, in the above-described example, the case where the reaction values t1 and t2 used for the failure diagnosis are obtained by the same calculation method as the reaction value t used for the comparison process in the inspection processing step (S120) has been described, but the present invention is not limited to this. do not have. Since it is only necessary to be able to diagnose the device failure, the reaction values t1 and t2 used for the diagnosis may be calculated by an algorithm different from the algorithm used for obtaining the reaction value t used for the comparison process in the original inspection processing step (S120). good.

In addition, although the description of parts that are not directly necessary for the description of the present invention, such as the device configuration and control method, is omitted, the required device configuration and control method can be appropriately selected and used. For example, the description of the control unit configuration for controlling the inspection device 100 has been omitted, but it goes without saying that the required control unit configuration is appropriately selected and used.

In addition, failure diagnosis methods and pattern inspection devices for all pattern inspection devices that include the elements of the present invention and can be appropriately redesigned by those skilled in the art are included in the scope of the present invention.

10 Inspection area 11 Sampling area 20 Inspection stripe 30 Frame area 50, 54, 68 Storage device 52 Frame image creation unit 56 Reaction value calculation unit 58 Comparison processing unit 72 Sampling area setting unit 80 Storage device 82 Defect undetected stripe number threshold setting unit 84 Judgment unit 86 Image reacquisition control unit 88 Judgment unit 100 Inspection device 101 Board 102 XYθ Table 103 Light source 104 Magnifying optical system 105 Photodiode array 106 Sensor circuit 107 Position circuit 108 Comparison circuit 109 Magnetic disk device 110 Control computer 112 Reference image creation Circuit 113 Autoloader control circuit 114 Table control circuit 116 GUI
117 External I / F
118 Pattern monitor 119 Printer 120 Bus 122 Laser length measurement system 123 Stripe pattern memory 140 Diagnostic circuit 150 Optical image acquisition mechanism 160 Control system circuit 170 Illumination optical system 174 Beam splitter 176 Imaging optical system

Claims (5)

A step of acquiring a first optical image of a predetermined region of the substrate before starting the pattern inspection of the substrate on which the pattern is formed by using the image acquisition mechanism of the pattern inspection apparatus.
A step of calculating the first value of a plurality of pixels of the first optical image using the acquired data of the first optical image of the predetermined region, and
A step of acquiring a second optical image of the predetermined region of the same substrate as the region of the first optical image during the pattern inspection of the substrate by using the image acquisition mechanism.
Using the acquired data of the second optical image in the predetermined region, the second value of the plurality of pixels of the second optical image is calculated by performing the same calculation as the calculation of the first value. And the process to do
When there is a pixel in which the difference between the first value of the plurality of pixels of the first optical image and the second value of the plurality of pixels of the second optical image is out of the range of the difference threshold. The process of determining the failure of the pattern inspection device and outputting the result,
A failure diagnosis method for a pattern inspection device, which is characterized by being equipped with. The method for diagnosing a failure of a pattern inspection apparatus according to claim 1, wherein a region including a defect portion in the region on which the pattern is formed is used as the predetermined region. The method for diagnosing a failure of a pattern inspection apparatus according to claim 1, wherein an arbitrary region of the regions on the substrate on which the pattern is formed is used as the predetermined region. The inspection area of the substrate is divided into a plurality of stripe areas.
The pattern inspection is performed for each stripe region of the plurality of stripe regions.
Claims 1 to 1, wherein a second optical image of the predetermined region is acquired after the number of stripe regions in which defects of the pattern formed on the substrate are no longer detected reaches a predetermined number. 3. The method for diagnosing a failure of the pattern inspection device according to any one of the above. Before starting the pattern inspection of the substrate on which the pattern is formed, the first optical image of a predetermined region of the substrate is acquired, and during the pattern inspection of the substrate, the same as the region of the first optical image. An image acquisition mechanism for acquiring a second optical image of the predetermined region of the substrate, and an image acquisition mechanism.
Using the acquired data of the first optical image of the predetermined region, the first values of the plurality of pixels of the first optical image are calculated, and the acquired second optics of the predetermined region are calculated. An arithmetic processing circuit that calculates the second value of a plurality of pixels of the second optical image by performing the same calculation as the calculation of the first value using the image data.
When there is a pixel in which the difference between the first value of the plurality of pixels of the first optical image and the second value of the plurality of pixels of the second optical image is out of the range of the difference threshold value. A determination processing circuit that determines that the pattern inspection device has failed, and
A pattern inspection device characterized by being equipped with.

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