JP2014115149A - Substrate inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate inspection device that is able to obtain a stable measurement result free from variations in a measurement value such as the inside diameter of a dent formed on the substrate.SOLUTION: A substrate inspection device 1 inspects a substrate 2 by using an image of the substrate 2 imaged by a microscope 4 and a camera 5 mounted on the microscope 4. The substrate inspection device 1 sets a specified area including a contact hole having a tapering part formed on the substrate 2, moves the focusing position of the microscope 4 relative to the depth direction of the substrate 2, and, at the same time, images the surface of the substrate 2 with the camera 5 for each preset imaging interval T, thereby obtaining a plurality of digital images. The substrate inspection device 1 calculates the edge width of a pair of edges detected in the specified area of each of the plurality of digital images, and outputs the smallest value among the calculated plurality of edge widths, as the value of the diameter of the bottom part of the contact hole.

Description

  The present invention relates to a substrate inspection apparatus for inspecting a substrate such as a liquid crystal glass substrate or a wafer.

Conventionally, in the inspection of a substrate such as a liquid crystal glass substrate, there is an inspection for measuring the line width of a pattern formed on the substrate.
In conventional inspection, an enlarged digital image of the substrate surface is acquired using a microscope and a camera such as a CCD camera mounted on the microscope, a differential value (contrast value) of luminance is obtained for each pixel, and the acquired digital image is contrasted. A pair of edges is clarified by converting to an image, and the distance between the edges is measured after making the pair of edges accurately recognizable. At this time, a digital image of the substrate surface is captured using, for example, a camera having a laser AF (Auto Focus) function or a contrast AF function.

  In a camera equipped with a laser AF function, the laser beam is directly irradiated onto the substrate surface, and the focus is on the position where the highest luminance is exhibited. For this reason, in the image captured by this camera, the position showing the highest luminance is clearly displayed, and the portion outside the in-focus position is unclear. For example, in the case of a substrate on which multiple patterns with different edge height positions are formed, such as a substrate on which patterns are stacked, the edge of the focused part is clearly displayed, and the edge is clearly displayed when converted to a contrast image. It is. On the other hand, an edge positioned above or below the focused edge is unclearly blurred as if blurred even when converted into a contrast image.

  In contrast, a plurality of tomographic images are taken at predetermined intervals while the microscope and camera are moved at a predetermined speed relative to the substrate from a state in which a part of the substrate surface is focused. Has been proposed (see, for example, Patent Document 1). In this method, each of a plurality of tomographic images is converted into a contrast image, and pixels having high contrast values at respective edges having different height positions are extracted from the respective contrast images, and these are combined to obtain a height position. A single contrast image in which the different edges are clearly projected is acquired.

On the other hand, in a camera equipped with a contrast AF function, an image can be acquired by adjusting the focal position so that the entire imaging area is clearly projected on average while changing the focal position within a range of heights of a plurality of edges. Done. As a result, even when a laminated pattern is provided, each edge is projected on average, and an extremely unclear edge can be eliminated.
It is also possible to measure the inner diameter of a depression such as a contact hole formed on a substrate using the various cameras as described above.

JP 2008-14646 A

However, the inner wall of the depression formed on the substrate is not formed along the direction perpendicular to the substrate plane, but the depression is formed so that the inner wall has a tapered surface. In some cases, the inner diameter or width of the bottom surface of the plate cannot be accurately determined. This is because, when the contrast AF function is used, it is determined that focusing is performed at any position of the tapered portion of the recess.
Therefore, there is a problem in that measurement results such as the inner diameter of the bottom surface portion vary.

  Therefore, an object of the present invention is to provide a substrate inspection apparatus that can obtain a stable measurement result without variations in measurement values such as the inner diameter of a recess formed on a substrate.

  A substrate inspection apparatus according to one aspect of the present invention is a substrate inspection apparatus that inspects the substrate using an image of the substrate captured by a microscope and a camera mounted on the microscope, and is a taper formed on the substrate. By setting a designated region including a hole or groove having a portion and moving the focal position of the microscope relative to the depth direction of the substrate, the surface of the substrate is set at each predetermined imaging interval. An image acquisition unit that captures a plurality of digital images captured by a camera; an edge width calculation unit that calculates an edge width of a pair of edges detected in each of the designated areas of the plurality of digital images; and the edge width A minimum edge width output unit that outputs a minimum value among a plurality of edge widths calculated by the calculation unit as a value of a diameter of a bottom surface of the hole or a width of a bottom surface of the groove; That.

  ADVANTAGE OF THE INVENTION According to this invention, the board | substrate inspection apparatus which can obtain the stable measurement result without variation in measured values, such as an internal diameter of the hollow formed on the board | substrate, can be provided.

It is a figure which shows the structure of the board | substrate inspection apparatus 1 which test | inspects a board | substrate based on embodiment of this invention. It is a top view of the contact hole which has a taper part formed on the board | substrate based on embodiment of this invention. It is sectional drawing of the board | substrate along the III-III line of FIG. It is a flowchart which shows the example of the flow of the process which measures the diameter of the bottom face part 21a of each context hole 21 formed in the predetermined position on the board | substrate 2 based on embodiment of this invention. 5 is a flowchart illustrating an example of a processing flow of S7 (image processing) in FIG. 4. It is a figure which shows the example of the image of the one part imaging region A on a board | substrate based on embodiment of this invention. It is a figure for demonstrating the relationship between the some tomographic image imaged with the camera 5, and the imaging position in a Z direction based on embodiment of this invention. It is a figure for demonstrating edge width dE acquired when the focus position of the microscope 4 exists in the middle position from the imaging start position Z1 to the imaging end position Zn based on embodiment of this invention. It is a graph which shows the example of the relationship between the focus position of the microscope 4, and the calculated edge width based on Embodiment of this invention. It is a figure for demonstrating edge width dE acquired when the focus position of the microscope 4 exists in the position of the bottom face part 21a based on embodiment of this invention. It is a top view of the groove | channel which has a taper part formed on the board | substrate based on embodiment of this invention. It is sectional drawing of the board | substrate along the XII-XII line | wire of FIG. It is a top view of the V-shaped groove which has the taper part formed on the board | substrate based on embodiment of this invention. It is sectional drawing of the board | substrate along the XIV-XIV line | wire of FIG.

Embodiments of the present invention will be described below with reference to the drawings.
(Constitution)
FIG. 1 is a diagram showing a configuration of a substrate inspection apparatus 1 for inspecting a substrate according to the present embodiment. The substrate inspection apparatus 1 includes a base 3 that movably supports a substrate 2, a microscope 4 having an objective lens 4a for observing the substrate surface 2a, and a CCD camera having a laser AF function, for example, mounted on the microscope 4. A support member 6 that supports the microscope 4 so that it can be moved up and down in the vertical direction (Z direction in this case), a drive mechanism 7 such as a motor for moving the support member 6 up and down, and the support member 6 For example, a measurement mechanism 8 such as a linear scale that identifies the position of the microscope 4 by detecting the amount is used as a main component. The substrate 2 is installed on an installation surface 3 a that is the upper surface of the base 3.
The camera 5 is connected to a captured image buffer memory device 9 for storing an image captured by the camera 5. The captured image buffer memory device 9 is connected to a monitor 10 as display means for displaying an image. Is connected. An arithmetic control device 11 is connected to the captured image buffer memory device 9, the drive mechanism 7, and the measurement mechanism 8. The arithmetic and control unit 11 converts the processed image buffer memory 12 for storing the digital image data sent from the captured image buffer memory device 9 and the digital image data into a contrast image, and based on the contrast value. And an image processing unit 13 for measuring the line width W. Furthermore, a work memory device 14 for storing the position of the microscope 4 measured by the measuring mechanism 8 is connected to the arithmetic control device 11.

As described above, the substrate inspection apparatus 1 is an apparatus that inspects a substrate using the image of the substrate 2 captured by the microscope 4 and the camera 5 mounted on the microscope 4.
In the present embodiment, the substrate 2 is a liquid crystal glass substrate. In this embodiment, a case will be described in which the inner diameter of the contact hole formed on the surface of the liquid crystal glass substrate, the inner wall of which has a tapered portion, is measured. The substrate may be a semiconductor wafer.

2 and 3 are diagrams for explaining a contact hole having a tapered portion formed on a substrate. FIG. 2 is a plan view of a contact hole having a tapered portion formed on the substrate. FIG. 3 is a cross-sectional view of the substrate along the line III-III in FIG.
As shown in FIGS. 2 and 3, the contact hole 21 is a depression having a predetermined depth, and has a circular bottom surface portion 21a at the center, and from a gently curved surface from the bottom surface portion 21a to the substrate surface 2a. It has the taper part 21b which becomes. The diameter of the bottom surface portion 21a is w. Hereinafter, the case where such a plurality of contact holes 21 are formed at predetermined positions on the substrate 2 and the diameter of the bottom surface portion 21a of each context hole 21 is measured will be described.
(Operation)
Next, the operation of the substrate inspection apparatus 1 will be described.
4 and 5 are flowcharts showing an example of a flow of processing for measuring the diameter of the bottom surface portion 21a of each context hole 21 formed at a predetermined position on the substrate 2. FIG. In particular, FIG. 5 is a flowchart showing an example of the processing flow of S7 (image processing) in FIG. 4 and 5 are executed by the arithmetic and control unit 11.
When an operation start command is input from the outside to the arithmetic and control unit 11, the arithmetic and control unit 11 first performs initial setting of predetermined set values such as the designated area number m, the moving speed v, and the imaging interval T (S1). ). The designated area number m is the number of contact holes to be measured on the surface 2 a of the substrate 2. The moving speed v is the speed of the microscope 4 when moving the microscope 4 in the Z direction. The imaging interval T is a time difference in imaging timing when imaging a contact hole. Here, it is assumed that the imaging intervals T are equal in the direction orthogonal to the substrate surface 2a.
Here, the imaging interval T is a time interval, but may be a moving distance of the focal position accompanying the movement of the microscope 4.

  In addition, in the initial setting, information such as an imaging region, an imaging start position in the Z direction when imaging a contact hole, and an imaging end position are also set. Here, it is assumed that imaging is performed n times at the imaging interval T from the imaging start position Z1, and the last imaging position is Zn.

  Next, the arithmetic and control unit 11 outputs a signal for the arithmetic and control unit 11 to rotate the driving mechanism 7 in either the forward or reverse direction, and the microscope 4 is moved to a preset initial position by driving the driving mechanism 7. . Here, the preset initial position is a position where the predetermined imaging area A of the substrate surface 2a can be imaged in a state where the surface 2a of the substrate 2 is focused, and is determined at the time of initial setting. Further, the arithmetic and control unit 11 focuses the substrate surface 2a placed on the base 3 by the laser AF function when the microscope 4 has moved to a preset initial position (S2).

  FIG. 6 is a diagram illustrating an example of an image of a part of the imaging region A on the substrate. In the imaging region A, a plurality (three in this case) of contact holes 21 are formed together with the wiring pattern 31. The focus is set on the substrate surface 2a of the imaging region A shown in FIG. In the imaging area A, a designated area Ei including at least the central portion of the contact hole 21 is set in advance as will be described later.

  Next, the arithmetic and control unit 11 moves the focal position of the objective lens 4a to the imaging start position Z1 (S3). Here, a position at a predetermined depth from the substrate surface 2a is defined as an imaging start position Z1. The imaging start position Z1 is set at a slightly deep position from the substrate surface 2a toward the bottom surface portion 21a.

  Next, the arithmetic and control unit 11 moves the microscope 4 downward along the Z direction which is perpendicular to the installation surface 3a of the substrate 2 at a preset moving speed v, and the digital image obtained by the camera 5 is obtained. Is started (S4). As a result, the focal position moves from the imaging start position Z1 toward the imaging end position Zn, and during this period, a plurality of images captured at different focal positions in the Z direction, which is the height direction, for each preset imaging interval T. Digital images (hereinafter referred to as tomographic images) are obtained.

  Therefore, the process of S4 sets the designated region Ei including the center portion of the contact hole 21 having the tapered portion 21b formed on the substrate 2, and the focus position of the microscope 4 is set with respect to the depth direction of the substrate 2. An image acquisition unit configured to acquire a plurality of digital images by imaging the surface of the substrate 2 with the camera 5 at each preset imaging interval T while moving relatively.

  The tomographic image captured by the camera 5 is stored in the captured image buffer memory 9 (S5), and the tomographic image stored in the captured image buffer memory 9 is displayed on the monitor 10 (S6).

  After the process of S5, the image process shown in FIG. 5 is executed (S6). The arithmetic and control unit 11 stores the tomographic image in the processed image buffer memory 13 (S11).

  Then, the arithmetic and control unit 11 executes a pattern matching process between the tomographic image stored in the processed image buffer memory 12 and the reference image of the design shape of the contact hole 21 (S12), and whether or not a predetermined pattern is detected. Is determined (S13). That is, in S13, the approximate position of the substrate 2 on the base 3 is specified, and at least one contact hole 21 for measuring the diameter of the bottom surface portion 21a is captured in the tomographic image, and the edge of the contact hole 21 It is confirmed whether the image is captured to such an extent that the width can be measured.

  When the contact hole 21 corresponding to the design shape is imaged and the edge of the contact hole 21 is imaged to such an extent that the diameter w of the bottom surface portion 21a can be measured (S13: YES), the arithmetic and control unit 11 is shown in FIG. As shown, edge detection areas (designated areas) Ei (i = 1 to 3 in FIG. 6) are set in the plurality of contact holes 21 so as to include a pair of edges, respectively (S14). In addition, when it is confirmed that the contact hole 21 is formed at a position substantially equal to the design shape by the pattern matching process with respect to the design shape of the contact hole 21, the designated region Ei is based on this design shape and the imaging region A Can be set by a relative position from the center C.

  Next, the arithmetic and control unit 11 performs edge clarification after converting the first image in each designated area Ei (i = 1 to 3) into a contrast image by differentiating with the image processing means 14. The contrast value in the designated area Ei is calculated and the edge is detected (S15).

  Then, the arithmetic and control unit 11 compares the contrast value dC of the edge of the tomographic image index number j (j = 1 in the first case) and the designated region number i (i = 1 in the first case) in the designated area Ei. = Contrast [i] [j]) is acquired (S16). Here, the index number j is an image number of tomographic images that are sequentially captured at every preset imaging interval T while the microscope 4 is moving downward from the imaging start position Z1 toward the imaging end position Zn. Means. In addition, since the focal length of the microscope 4 with respect to the substrate 2 is measured by the measurement mechanism 8 at the time of capturing the tomographic image, the imaging height position of the tomographic image with respect to the substrate 2 can be specified by this index number j.

  Next, the arithmetic and control unit 11 checks whether or not the edges in the designated area Ei are detected as a pair of edges (S17). At this time, when the contrast value of one edge is acquired and the contrast value of the other edge cannot be acquired, for example, the height position of each edge is shifted in a pair of edges of the designated area Ei. Becomes impossible to measure the diameter of the contact hole 21. Therefore, it is confirmed whether the contrast values of the pair of edges included in the designated area Ei are detected.

  When the pair of edges is detected (S17: YES), the arithmetic and control unit 11 measures the distance between the pair of edges by the image processing unit 13 and acquires the edge width dE of the contact hole 21 (S18). That is, the processing of S18 constitutes an edge width calculation unit that calculates the edge width of a pair of edges detected in each designated area Ei of a plurality of digital images.

If a pair of edges is not detected (S17: NO), the process proceeds to S19.
Next, after obtaining the edge width dE of one designated area Ei, it is confirmed whether or not the designated area number i matches the designated area number m, and the edge width dE is obtained for all the designated areas Ei. Is confirmed (S19). If the designated area number i does not match the designated area number m (S19: NO), there is a designated area Ei for which the acquisition of the edge width dE has not yet been completed, and therefore the contrast of the edges of the remaining designated area Ei. When the values are sequentially acquired and a pair of edges are detected in the same manner as described above, the edge width dE is acquired (S16 to S18).

  When the processing is completed for all the designated areas Ei of one tomographic image (S19: YES), the index number j is incremented by one in order to capture the next tomographic image, that is, j = j + 1. (S8).

  Next, the arithmetic and control unit 11 determines whether or not the tomographic image processed immediately before has been captured at the imaging end position Zn (S9). When the tomographic image processed immediately before is not captured at the imaging end position Zn (S9: NO), the process returns to S5, and until the acquisition of the edge width dE of the tomographic image at the imaging end position Zn is completed, the process returns to S5. To S8 are executed.

  In the pattern matching stage (S12, S13), when the contact hole 21 corresponding to the design shape is not captured at all in the tomographic image or when the edge width can be determined, the tomographic image is used. The inspection is terminated, and the process proceeds to the processing of the tomographic image with the next index number j.

  If YES in S9, the arithmetic and control unit 11 moves the focal position of the microscope 4 from the imaging start position Z1 to the imaging end position Zn, completes the tomographic image imaging operation, and finishes processing of all the tomographic images. At the stage, the acquisition of the contrast value of the pair of edges in each designated area Ei in each tomographic image and the data of the edge width dE measured in each contrast state is completed.

  Therefore, the arithmetic and control unit 11 extracts a digital image that maximizes the contrast value of the pair of edges in each designated area Ei, extracts a digital image that minimizes the pair of edge widths dE (S10), and extracts the digital image. The inspection result with the edge width dE measured in the digital image as the diameter of the bottom surface portion 21a is output (S11).

Here, the imaging positions of a plurality of tomographic images obtained by the above-described processing and the edge width of the contact hole will be described.
FIG. 7 is a diagram for explaining a relationship between a plurality of tomographic images captured by the camera 5 and imaging positions in the Z direction. Although the substrate 2 is imaged by the objective lens 4a, the focal position of the microscope 4 moves from the imaging start position Z1 to the imaging end position Zn. As a result, n tomographic images CI from the tomographic image CI1 at the imaging start position Z1 to the tomographic image CIn at the imaging end position Zn are imaged, and the imaging operation is stored in the processed image buffer memory 13.

  FIG. 8 is a diagram for explaining the edge width dE acquired when the focus position of the microscope 4 is in the middle position between the imaging start position Z1 and the imaging end position Zn. As shown in FIG. 8, when the objective lens 4a is focused at a position where the tapered portion 21b is located by the laser AF function, the edge width dE calculated in S18 is w1.

  The imaging start position Z1 is located between the bottom surface portion 21a of the contact hole 21 formed on the substrate 2 and the substrate surface 2a in the Z direction, and the imaging end position Zn is located from the substrate surface 2a to the bottom surface portion 21a. A deeper position. Therefore, while the focus position of the microscope 4 moves from the imaging start position Z1 to the imaging end position Zn, the focus position of the microscope 4 passes through the position of the bottom surface portion 21a.

  FIG. 9 is a graph showing an example of the relationship between the focal position of the microscope 4 and the calculated edge width. As shown in FIG. 9, the edge width dE calculated and acquired while the focal position of the microscope 4 moves from the imaging start position Z1 to the imaging end position Zn becomes smaller as the focal position becomes deeper from the substrate surface 2a. However, the edge width dE increases as the focal position passes the position of the bottom surface portion 21a and becomes deeper.

  In FIG. 9, the edge width dE is minimum when the focal position is the imaging position Zk at the position of the bottom surface portion 21a. That is, when the focus position of the microscope 4 is at the position of the bottom surface portion 21a of the tapered portion 21, the edge width dE is the smallest.

  FIG. 10 is a diagram for explaining the edge width dE acquired when the focus position of the microscope 4 is at the position of the bottom surface portion 21a. As shown in FIG. 10, when the objective lens 4a is focused on a certain position of the bottom surface portion 21a by the laser AF function, the edge width dE calculated in S18 is w.

  Therefore, the edge width dE output in S10 and S11 of FIG. 4 described above is the diameter of the bottom surface portion 21a of the contact hole 21.

  Therefore, the processing of S11 is performed by setting the minimum edge width output unit to be output using the minimum value among the plurality of edge widths calculated in S18 as the edge width calculation unit as the value of the diameter of the bottom surface portion 21a of the contact hole 21. Configure.

  As described above, according to the substrate inspection apparatus of the above-described embodiment, the substrate inspection apparatus can obtain a stable measurement result without variation in the measured value of the inner diameter of the bottom surface portion of the contact hole formed on the substrate. Can be provided.

  In the above-described embodiment, the example of measuring the diameter of the bottom surface portion of the contact hole has been described. However, in the case of measuring the width of the bottom surface portion of the groove in the groove having the tapered portion, the above-described substrate inspection apparatus is also provided. Can be applied.

11 and 12 are diagrams for explaining a groove having a tapered portion formed on a substrate. FIG. 11 is a plan view of a groove having a tapered portion formed on a substrate. 12 is a cross-sectional view of the substrate along the line XII-XII in FIG.
As shown in FIGS. 11 and 12, the groove 41 has a predetermined depth, has a linear bottom surface portion 41a along the groove at the center, and gently on both sides from the bottom surface portion 41a to the substrate surface 2a. It has a tapered portion 41b made of a curved surface. The width of the bottom surface portion 41a is ww. By calculating the edge width in the designated region set so as to include the groove while changing the focal position in the Z direction, the edge width at the smallest can be measured as the width of the bottom surface of the groove.

  Therefore, in the case of FIG. 11 and FIG. 12, S11 as the minimum edge width output unit uses the minimum value among the plurality of edge widths calculated in S18 as the edge width calculation unit as the value of the width of the bottom surface of the groove. Output as.

  Further, in the measurement of the diameter of the bottom surface or the width of the groove in the contact hole 21 or the groove 41 described above, the minimum edge width dE is used as the measured value. From the focal position when the edge width dE is calculated, the depth of the bottom surface portion can also be measured. That is, from the distance between the position of the substrate surface 2a detected in S2 and the imaging start position Z1, and the distance between the imaging start position Z1 and the focal position when the minimum edge width dE is detected, the depth of the contact hole 21 or the groove 41 is determined. Can be calculated.

Further, in the case of a groove having no bottom surface, for example, a groove having a V-shaped cross section, the depth of the deepest position of the groove can be measured.
13 and 14 are plan views for explaining a V-shaped groove formed on the substrate 2. FIG. 13 is a plan view of a V-shaped groove having a tapered portion formed on the substrate. FIG. 14 is a cross-sectional view of the substrate along the line XIV-XIV in FIG.
As shown in FIGS. 13 and 14, the groove 51 has a predetermined depth dd, and has a tapered portion 51 a that is an inclined surface toward the center of the groove 51. The width of the groove 51 is v. The focal point from the surface 2a corresponding to the smallest edge width (almost 0 (zero)) is calculated by calculating the edge width in the specified region set to include the groove while changing the focal position in the Z direction. The distance (dd) to the position can be measured as the depth of the central portion of the groove 51. That is, the depth of the groove 51 is calculated from the distance between the position of the substrate surface 2a detected in S2 and the imaging start position Z1, and the distance between the imaging start position Z1 and the focal position when the minimum edge width dE is detected. be able to.

  Therefore, in the above case, the process of S11 is performed when a digital image in which the minimum value among the plurality of edge widths calculated in S18 as the edge width calculation unit is obtained from the surface 2a of the substrate 2 is captured. A distance output unit for outputting a distance value to the focal position of Then, the benefit output unit can output the depth value of the bottom surface portions 21 a and 41 a of the contact hole 21 or the groove 41 or the depth value of the groove 51.

That is, according to the substrate inspection apparatus of the above-described embodiment, the substrate inspection apparatus can obtain a stable measurement result with no variation in the measured value of the depth of the deepest position of the recess or groove formed on the substrate. Can also be realized.
As described above, according to the above-described embodiment, it is possible to provide a substrate inspection apparatus that can obtain a stable measurement result without variations in measurement values such as the inner diameter of a recess formed on a substrate.

  The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the scope of the present invention.

1 substrate inspection device, 2 substrate, 2a substrate surface, 3 base, 3a installation surface, 4 microscope, 4a objective lens, 5 camera, 6 support member, 7 drive mechanism, 8 measurement mechanism, 9 buffer memory device for captured image, DESCRIPTION OF SYMBOLS 10 Monitor, 11 Computation control apparatus, 12 Processed image buffer memory, 13 Image processing part, 14 Work memory device, 21 Contact hole, 21a Bottom face part, 21b Taper part, 31 Wiring pattern, 41 Groove, 41a Bottom face part, 41b Taper Part, 51 groove, 51a taper part.

Claims (3)

A substrate inspection apparatus for inspecting the substrate using an image of the substrate imaged by a microscope and a camera mounted on the microscope,
An imaging interval is set in advance while setting a designated region including a hole or groove having a tapered portion formed on the substrate, and moving the focal position of the microscope relative to the depth direction of the substrate. An image acquisition unit for acquiring a plurality of digital images by imaging the surface of the substrate with the camera every time;
An edge width calculator that calculates an edge width of a pair of edges detected in each of the designated areas of the plurality of digital images;
A minimum edge width output unit that outputs a minimum value among a plurality of edge widths calculated in the edge width calculation unit as a value of a diameter of a bottom surface part of the hole or a width of a bottom surface part of the groove;
A board inspection apparatus comprising:   The substrate inspection apparatus according to claim 1, wherein the hole is a contact hole formed on the substrate.   The substrate inspection apparatus according to claim 1, wherein the substrate is a liquid crystal glass substrate or a semiconductor wafer.

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