JP2007163259A - Difference comparison inspection method and difference comparison inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a difference comparison inspection method and a difference comparison inspection device capable of performing proper comparison inspection even in the case of a pattern having an angular part or a corner part. <P>SOLUTION: An internal angle which is a recessed corner and an external angle which is a projecting angle formed on the pattern are detected respectively from a master image. Then, a range of an internal angle domain which is a domain near the detected internal angle is determined. Also, a range of an external angle which is a domain near the detected external angle is determined. Then, comparison inspection is performed based on a difference between the master image and an object image. In this case, the comparison inspection is performed by excluding a difference to an excessive domain which is a pattern domain of the object image formed more excessively than a pattern domain shown by the master image in the internal angle domain of the master image. The comparison inspection is performed by excluding a difference to the pattern domain of the object image formed more deficiently than the pattern domain shown by the master image in the external angle domain of the master image. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a differential comparison inspection method and apparatus using an image obtained by imaging an object to be inspected, and more specifically to a comparison inspection method and apparatus for a pattern formed on a substrate.

  On the surface of the printed circuit board on which electronic components and the like are mounted, a conductor wiring necessary for constituting a predetermined circuit is formed in a pattern. One of the wiring pattern inspection methods is a comparative inspection method. This is a method in which a non-defective image created from CAD data is compared with an inspection image obtained by imaging a substrate to be inspected, and a portion having a certain difference or more is detected as a defect. Specifically, the comparative inspection method is based on a difference in the number of pixels between a master image, which is an image obtained by converting CAD data into a digital image, and an inspection image obtained by capturing an inspection object (inspection object) and converting it into a digital image. Detect defects. Typically, if this difference value is greater than or equal to a predetermined value, the inspection object is a defect. FIG. 21 is a diagram for explaining such a comparative inspection method. In FIG. 21, a CAD data master pattern image (FIG. 21A) is converted into a binarized digital image (FIG. 21B). Similarly, an image obtained by imaging an inspection pattern to be inspected (FIG. 21C) is also converted into a binarized digital image (FIG. 21D). Then, the two digital images are compared, and a difference value for each pixel is calculated (FIG. 21E). If the difference value is equal to or greater than a predetermined value, the inspection object is considered defective.

  However, since the wiring pattern formed on the surface of the printed circuit board is produced through a chemical treatment process such as etching, it is particularly susceptible to etching at corners and corners. For example, "over-etching" where the tip of the convex part is rounded at the convex corner (outer corner) of the figure (pattern area), or the inside of the concave part is rounded at the concave corner (inner corner) of the figure A phenomenon called “under etching” occurs (see FIG. 22). The pattern region formed by such over-etching or under-etching is detected as a defective portion because it is determined that there is a difference from the master image in the comparative inspection method described above. On the other hand, such differences in corners and corners due to etching often do not pose a major problem in the performance of printed circuit boards. Therefore, it is desirable that a pattern region formed by such overetching or underetching is not detected as a defect. That is, in the comparative inspection of the wiring pattern formed on the surface of the printed circuit board, the sensitivity of the comparative inspection should be increased for the linear portion of the pattern, and the sensitivity of the comparative inspection should be decreased for the edge portions such as corners and corners. Is required.

As a method for preventing the above-described over-etching or the like from being detected as a defect, there is a method of inspecting the entire surface of the printed circuit board by setting a high allowable value as a difference value. There is also a method in which an inner angle and an outer angle are detected from a master image, and an inspection is performed by setting a high allowable value (that is, lowering the sensitivity of the comparative inspection) for a certain range around the master image. That is, there is also a method in which only the periphery of the inner corner portion and the outer corner portion is not determined as a defect even if the difference value is relatively large. In addition, there is a method in which a corner image is rounded (outside corner) in advance for the outer corner portion and a master image is prepared in advance for the inner corner portion and compared with the inspection image (for example, Patent Document 1). Furthermore, as another method, there is a method of removing the inner corner portion and the outer corner portion from the target of the comparative inspection (for example, Patent Document 2).
Japanese Patent Laid-Open No. 11-143052 JP-A-61-86639

  However, in the case of the method disclosed in Patent Document 1 described above, all the corners and corners of the pattern area to be inspected are not necessarily in the same shape as the master image obtained by rounding the corners and corners in advance. Absent. This is because the shape of corners and corners in the pattern region to be inspected may change depending on the etching state. Therefore, although detection of defects due to overetching or underetching is somewhat reduced, it is still detected as a defect. Also, when increasing the tolerance value of the defect judgment condition only for corners and corners (decreasing sensitivity), it is necessary to prepare two types of tolerance values for judgment, corners and corners and other parts. There is. For this reason, a plurality of allowable value determination circuits are required, which is expensive. In addition, in the case of the method disclosed in Patent Document 2 described above, defects due to over-etching or under-etching are certainly not detected, but corners and corners are not inspected in the first place. Even if a defect that causes a problem in the performance of the printed circuit board occurs at the corner, it cannot be detected as a defect.

  Therefore, an object of the present invention is to provide a difference comparison inspection method and a difference comparison inspection apparatus that can perform an appropriate comparison inspection even for a pattern having corners and corners.

  In order to achieve the above object, the present invention employs the following configuration.

  A first invention is a differential comparison inspection method for inspecting an inspection object by comparing an object image obtained by imaging an inspection object on which a pattern is formed with a master image of the pattern, and a corner detection step , An inner angle area determining step, an outer angle area determining step, and a comparative inspection step. In the corner detection step, an inner angle that is a concave corner formed in the pattern and an outer angle that is a convex corner are detected from the master image. In the interior angle area determination step, a range of the interior angle area that is an area in the vicinity of the detected interior angle is determined. In the outer angle area determination step, a range of the outer angle area that is an area in the vicinity of the detected outer angle is determined. In the comparison inspection step, a comparison inspection is performed based on a difference between the master image and the object image. In the comparison inspection step, a comparison inspection is performed by excluding a difference with respect to the pattern area of the object image formed excessively in the inner corner area of the master image from the pattern area indicated by the master image. Further, in the outer corner area in the master image, a comparison inspection is performed by excluding a difference from the pattern area of the object image formed in a shortage than the pattern area indicated by the master image.

  In a second aspect based on the first aspect, the object image and the master image are different from the first value in the pixel value of the area where the pattern is formed, and the other pixel values are different from the first value. It is the binarized image used as the second value. The inner angle area determination step includes an inner angle area image generation step of generating an inner angle area image in which the pixel value in the inner angle area is the first value and the pixel value outside the inner angle area is the second value. In addition, the outside angle area determining step includes an outside angle area image generating step for generating an outside angle area image in which the pixel value in the outside angle area is the first value and the pixel value outside the outside angle area is the second value. The comparison inspection step includes an alignment step for aligning the master image, the inner angle area image, the outer angle area image, and the object image on the same coordinate axis, and the pixel at the inspection target position that is the same position on the coordinate axis. A pixel value acquisition step for acquiring a pixel value from each image, the pixel value of the acquired object image is the first value, the pixel value of the acquired master image is the second value, and the acquired inner angle region When the pixel value of the image is the first value, the master image at the inspection target position and the pixel value of the object image are compared and inspected, and the pixel value of the acquired object image is the second value, When the pixel value of the acquired master image is the first value and the pixel value of the acquired outer-angle region image is the first value, the master image and the offset of the inspection target position are displayed. Comparing the inspection pixel values of the object image as the same value.

  In a third aspect based on the first aspect, the angle detection step detects one pixel indicating the inner angle or the outer angle from the master image, and the inner angle region determination step centers on the pixel that is the detected inner angle. A region having a predetermined size is determined as the inner corner region, and the outer corner region determining step determines a region having a predetermined size centered on the detected pixel having the outer corner as the outer corner region.

  In a fourth aspect based on the third aspect, the inner angle area determining step determines the inner angle area by repeatedly performing the expansion process a predetermined number of times or more on the detected inner angle pixels, In the outer corner area determination step, the outer corner area is determined by repeatedly performing the expansion process on the detected outer corner pixels by a predetermined number of times or more.

  According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the method further includes a width detecting step of detecting a width of the linear portion of the pattern close to the detected inner angle or outer angle. The inner corner area image generation step changes the number of times of repeating the expansion process according to the detected width, and the outer angle area image generation step changes the number of times of repeating the expansion process according to the detected width.

  In a sixth aspect based on the third aspect, the corner detection step uses a plurality of patterns each indicating a pixel value of the target pixel in the master image and a plurality of pixel positions extracted based on the target pixel. It further includes a logical operation step of detecting that the pixel of interest is one pixel indicating an inner angle or an outer angle using a pixel value extracted from the image and a predetermined logical expression. The logical operation step indicates that the operation result of a predetermined logical expression in which the pixel value extracted using any one of the patterns and the pixel value of the target pixel is substituted is an interior angle or an exterior angle. In this case, the target pixel is detected as one pixel indicating the inner angle or the outer angle.

  In a seventh aspect based on the third aspect, the corner detection step is performed using a plurality of patterns each indicating a pixel value of a target pixel in the master image and positions of a plurality of pixels extracted based on the target pixel. It further includes a logical operation step for detecting that the pixel of interest is one pixel indicating an internal angle or an external angle using the pixel value extracted from the image, and the logical operation step includes a pixel value of the pixel of interest as a master image. When the pixel value of the target pixel is different from all the pixel values extracted using any one of the patterns, the target pixel is one pixel indicating an outer angle. And the pixel value of the target pixel indicates outside the pattern area indicated by the master image, and the pixel value of the target pixel is all extracted using any one of the patterns. When made, it is detected as the target pixel is a pixel showing the interior angle.

  An eighth invention is a differential comparison inspection apparatus that inspects an inspection object by comparing an object image obtained by imaging the inspection object on which a pattern is formed with a master image of the pattern, , An inner angle region determination unit, an outer angle region determination unit, and a comparison inspection unit. The corner detection unit detects an inner angle, which is a concave corner, and an outer angle, which is a convex corner, formed in the pattern from the master image. The interior angle area determination unit determines the range of the interior angle area that is an area in the vicinity of the detected interior angle. The outside angle area determination unit determines a range of the outside angle area, which is an area in the vicinity of the detected outside angle. The comparison inspection unit performs a comparison inspection based on a difference between the master image and the object image. In addition, the comparative inspection unit performs a comparative inspection by excluding a difference with respect to the pattern area of the object image that is formed excessively in the inner corner area of the master image from the pattern area indicated by the master image. In addition, the comparison inspection unit performs a comparative inspection by excluding a difference with respect to the pattern area of the object image formed in the outer corner area of the master image that is less than the pattern area indicated by the master image.

  According to the first aspect, even if there is a location that does not match between the master image and the object image, the sensitivity (inspection accuracy) of the comparative inspection can be changed depending on whether the location is an internal angle or an external angle. That is, for the inner corner portion of the object image, even if there is an excess portion than the master image, it does not take a difference for that portion, and as a result, it is possible to prevent false reports that the portion is reported as a defect, Even for the same inner corner portion, a difference is taken for a portion that should originally be reported as a defect, and is reported as a defect. In addition, even if there is a portion that is lacking with respect to the master image in the outer corner portion of the object image, the difference is not taken for the portion, and as a result, false information that is reported as a defect for the portion can be prevented. . On the other hand, even for the outer corner portion, a difference is taken for a portion that should be reported as a defect and is reported as a defect. Thereby, it becomes possible to detect an appropriate defect according to the shape of the corner of the print pattern which tends to be miscellaneous. In addition, as in the prior art, it is not necessary to perform inspection by setting a high value around the inner corner and the outer corner so as not to be determined as a defect even if the difference value is relatively large. That is, the threshold value of the difference value reported as a defect can be reduced. Therefore, the threshold value of the difference value is set low, and a high sensitivity comparison inspection is performed as a whole, but parts that are not desired to be detected as defects such as under etching and over etching are detected as defects. Can be prevented. As a result, a highly accurate comparative inspection is possible.

  According to the second aspect, since a binarized image is used, a simple logic determination process using a combination of 0 and 1, for example, can be performed, and the processing speed can be increased.

  According to the third aspect of the invention, the area centered on the detected inner angle or outer angle pixel is defined as the inner angle area or the outer angle area. Thereby, it is possible to carry out a comparative inspection that is universally compatible with various shapes such as an inner angle and an outer angle due to an etching factor or the like.

  According to the fourth aspect of the invention, the detected inner angle or outer angle pixel is expanded in the vicinity to obtain the inner angle region or the outer angle region. Thereby, since a substantially circular area can be generated, an inner angle area and an outer angle area that can correspond to various corner and corner shapes can be generated.

  According to the fifth aspect of the invention, the number of expansion stages of the pixels at the inner angle and the outer angle is changed according to the detected width of the linear portion of the pattern close to the outer angle or the inner angle. Thereby, it is possible to generate an inner corner region and an outer corner region according to the width of the straight line portion, and it is possible to perform a comparative examination with higher accuracy and higher accuracy.

  According to the sixth to seventh aspects of the present invention, the pixels indicating the inner angle or the outer angle are detected using a predetermined pattern and logical expression. Therefore, by performing uniform and simple determination processing for each pixel of the master image, the inner angle or the outer angle can be detected, and the processing speed can be increased and the processing load can be reduced.

  Further, according to the comparative inspection apparatus of the present invention, the same effect as that of the first invention described above can be obtained.

  Hereinafter, a differential comparison inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing an overall configuration of an optical appearance inspection apparatus 1 (hereinafter referred to as an inspection apparatus 1) which is an example of the difference comparison inspection apparatus. 1A is a top view of the inspection apparatus 1, and FIG. 1B is a front view of the inspection apparatus 1. FIG. In FIG. 1, the inspection apparatus 1 includes a stage unit 11, a stage support unit 12, a stage drive mechanism 13, a base unit 14, an imaging camera 15, a support member 16, a camera support unit 17, and a camera drive mechanism 18.

  The stage unit 11 constitutes a horizontal stage surface on the top surface. The printed wiring board S that is the object to be inspected is placed on the stage surface of the stage unit 11. The lower part of the stage unit 11 is supported by a stage support unit 12. The stage support 12 is fixed on the upper surface of the stage drive mechanism 13. The base portion 14 is parallel to the stage surface and extends and fixed in the illustrated Y-axis direction (main scanning direction). The stage drive mechanism 13 is slidably installed along a guide provided on the upper surface of the base portion 14 so as to extend in the Y-axis direction. That is, the stage drive mechanism 13 and the stage support part 12 and the stage part 11 fixed on the stage drive mechanism 13 are movable in the Y-axis direction.

  The support member 16 is installed in the upper space of the stage unit 11. On the support member 16, there is provided a camera drive mechanism 18 that extends in the illustrated X-axis direction (sub-scanning direction) parallel to the stage surface and perpendicular to the Y-axis direction. The camera support unit 17 is connected to the camera drive mechanism 18 and is disposed so as to be capable of reciprocating along the X-axis direction. The imaging camera 15 is supported by the camera support 17 so that the imaging direction is vertically downward (downward in the Z axis in the drawing). The imaging camera 15 is constituted by a CCD camera, for example, and converts incident light into an electrical signal indicating its color and intensity to generate an image of the captured printed wiring board S.

  The inspection apparatus 1 captures an image of the printed wiring board S with the imaging camera 15 and acquires an image of the upper surface of the printed wiring board S. At this time, in order to acquire an image of the entire surface of the printed wiring board S, the inspection apparatus 1 moves the stage unit 11 in the Y-axis direction and moves the imaging camera 15 in the X-axis direction. Specifically, main scanning is performed by moving the stage unit 11 in the Y-axis direction while the position of the imaging camera 15 in the X-axis direction is fixed. Here, every time main scanning from one end to the other end of the substrate S is completed, the imaging camera 15 moves by a predetermined distance along the sub-scanning direction (X-axis direction). As a result, an image of the entire surface of the printed wiring board S including the print pattern for the entire inspection area of the printed wiring board S can be obtained by the imaging camera 15.

  FIG. 2 is a block diagram showing a functional configuration of the inspection apparatus 1. In FIG. 2, the inspection apparatus 1 includes a control unit 21, an object image generation unit 22, a corner area image generation unit 23, a storage unit 26, and a comparison inspection unit 31 in addition to the components described above.

  The control unit 21 is configured by, for example, a CPU board. The control unit 21 is connected to each component described below. The control unit 21 also controls the entire inspection process according to the present embodiment, such as data input / output to / from the storage unit 26, operation control of the imaging camera 15, and various image processing.

  The object image generation unit 22 binarizes the image captured by the imaging camera 15. Here, it is assumed that, among the pixels constituting the image captured by the imaging camera 15, a pixel having a density higher (darker) than a predetermined threshold is set to 1, and the remaining pixels are set to 0 to be binarized. Of course, a pixel having a density higher than a predetermined threshold may be set to 0 and the remaining pixels may be set to 1. Further, the object image generation unit 22 stores the object image 27 that is the binarized image in the storage unit 26.

  The corner area image generation unit 23 includes a corner detection unit 24 and an expansion unit 25. The angle detection unit 24 reads the master image 28 stored in the storage unit 26 and detects the positions of the inner angle and the outer angle from the master image 28. The expansion unit 25 determines an internal angle region and an external angle region by expanding (enlarging) one pixel on the master image corresponding to the position of the internal angle and the external angle detected by the angle detection unit 24 by a predetermined number of steps. Then, an inner angle area image 29 and an outer angle area image 30 respectively indicating the inner angle area and the outer angle area are generated and stored in the storage unit 26.

  The storage unit 26 is, for example, a storage medium such as a semiconductor memory or a hard disk, and the object image 27, a master image 28 created in advance based on CAD data, an inner angle region image 29 and an outer angle generated by the expansion unit 25. A region image 30 (details will be described later) is stored. Although not shown, various flags and the like used in the comparison inspection process described later are also stored in the storage unit 26.

  The comparison inspection unit 31 performs a comparison inspection between the object image 27 and the master image 28 using the inner corner area image 29 and the outer corner area image 30 stored in the storage unit 26.

  Note that the control unit 21, the object image generation unit 22, the corner area image generation unit 23, and the comparative inspection unit 31 illustrated in FIG. 2 may be realized as an LSI that is typically an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible.

  Next, an outline of the comparison inspection process in the present embodiment will be described. In the present embodiment, basically, a master image 28 that is a binarized image generated from CAD data, and an object image 27 that is generated by imaging the inspection target and binarizing in the same manner. A comparison inspection process is performed by comparison. Here, in order to make the description more specific, a portion within the print pattern area is set to 1 (with dots), and a section outside the area is set to 0 (without dots).

  FIG. 3A is a diagram illustrating an example of the master image 28, and FIG. 4 is a diagram illustrating an example of the object image 27. When these two images are simply compared, in the object image 27 of FIG. 4, an under-etched portion 41 (a region formed in excess of the pattern region indicated by the master image 28) and an over-etched portion 42 (the master image 28 shows) The area that is formed less than the pattern area does not match the master image 28.

  Therefore, before the comparison inspection is performed, image data for identifying the inner angle and the outer angle, that is, the inner angle region image 29 and the outer angle region image 30 are generated. Specifically, from the master image 28, an inner angle (diamond mark in FIG. 3 (A)) that is a concave corner formed in a pattern by a method as described later and an outer angle (FIG. 3 (A) that is a convex corner). Each pixel indicating ()) is detected. Next, the detected one pixel is expanded by 8 by a predetermined number of stages. That is, by expanding one detected pixel to a plurality of pixels centered on the one pixel, a region near the detected one pixel is generated as an inner corner region or an outer corner region. Then, as shown in FIG. 3B, image data 29 is generated in which the inner angle area obtained by enlarging one pixel of the detected inner angle is set to 1, and the other areas are set to 0 (this becomes the inner angle area image 29). ). In addition, as shown in FIG. 3C, image data 30 is also generated in which the outside angle region obtained by enlarging one pixel of the detected outside angle is set to 1, and the other region is set to 0 (this corresponds to the outside angle region image 30 and Become). In FIGS. 3A to 3C, 1 (with dots) is shown as a black area, and 0 (without dots) is shown as a white area. When the master image 28 and the object image 27 are compared and inspected, for example, when a certain pixel is compared, if there is a difference between the master image 28 and the object image 27, the inner angle region image 29 and the outer angle With reference to the region image 30, it is determined whether the pixel having the difference is included in the inner corner region or the outer corner region. As a result, when the pixel is included in the inner corner region, if the pixel is an under-etched portion (an excessively formed region), no difference is taken for the pixel, but the pixel is an over-etched portion ( If it is an area that is insufficiently formed, the difference is taken. On the other hand, when the pixel is included in the outer corner region, the difference is not taken if the pixel is an over-etched portion, but the difference is taken for the pixel if the pixel is an under-etched portion. Then, if the final difference value exceeds a predetermined allowable value, it is determined that there is a defect.

  FIG. 5 is a diagram showing the principle of comparative inspection in the present embodiment. In FIG. 5, the inspection target pixel value 51 indicates the pixel values of the master image 28 and the object image 27 for the inspection target pixel. In the pixel value, 0 indicates that there is no pixel, and 1 indicates that there is a pixel. The presence / absence 52 of the difference indicates the presence / absence of a difference between the master image 28 and the object image 27 relating to the pixel. 0 indicates that there is no difference, and 1 indicates that there is a difference.

  In FIG. 5, for example, when the master image 28 and the object image 27 are both 0 for the pixel value of a predetermined pixel, it is determined that there is no difference (0) with respect to all of the outer angle area, the inner angle area, and the normal area. Is done. Similarly, when both the master image 28 and the object image 27 are 1, it is determined that there is no difference for all (0).

  On the other hand, when the pixel value of the master image 28 relating to the pixel to be inspected is 0 and the pixel value of the object image 27 is 1, it is determined that there is a difference (1) when the pixel is in the outer corner area and the normal area. The However, when the pixel is in the inner corner area, it is determined that there is no difference (0). That is, the under-etched portion 41 shown in FIG. 4 is not determined to have a difference. On the other hand, even if the pixel is included in the inner corner area, if the pixel value of the master image 28 is 1 and the pixel value of the object image 27 is 0, that is, the over-etched portion in the inner corner area is determined to have a difference. Is done.

  When the pixel value of the master image 28 relating to the pixel to be inspected is 1 and the pixel value of the object image 27 is 0, it is determined that there is a difference (1) when the pixel is in the inner corner area and the normal area. The However, when the pixel is in the outer corner area, it is determined that there is no difference (0). That is, it is not determined that there is a difference in the over-etched portion 42 shown in FIG. On the other hand, even if the pixel is included in the outer corner area, if the pixel value of the master image 28 is 0 and the pixel value of the object image 27 is 1, that is, the under-etched portion in the outer corner area is determined to have a difference. Is done. As described above, in this embodiment, the difference detection criterion is changed according to whether there is a difference between the master and the object, depending on whether the difference is the inner corner region, the outer corner region, or the normal region.

  The detailed operation of the comparison inspection process performed by the inspection apparatus 1 will be described below with reference to FIGS. First, prior to the comparison inspection process, a preparation process for preparing various images used for the above-described comparison inspection is performed. FIG. 6 is a flowchart showing details of the preparation process.

  In FIG. 6, first, an inner corner area image generation process (step S1) for generating the inner corner area image 29 is performed. Subsequently, an outside angle area image generation process (step S2) for generating the outside angle area image 30 is performed. The order in which these processes are performed may be reversed, or may be performed in parallel. Here, the interior angle in the present embodiment is, for example, a concave corner formed in the print pattern as shown in FIG. 7, and one corner pixel located outside the print pattern area is defined as the interior angle. It is called a point (pixels with diamonds in FIG. 7). In addition, the outer angle is a convex corner formed in the print pattern as shown in FIG. 7, and one corner pixel located in the print pattern region is called an outer angle point (see FIG. 7). Star pixel).

  FIG. 8 is a subroutine showing details of the inner corner area image generation processing shown in step S1. In FIG. 8, first, the control unit 21 causes the corner detection unit 24 to read the master image 28 that is generated in advance and stored in the storage unit 26 (step S <b> 11).

Subsequently, the corner detection unit 24 detects the inner corner point from the read master image 28 (step S12). The process of step S12 will be described more specifically. First, the corner detection unit 24 determines, from each pixel of the master image 28, one pixel (hereinafter referred to as a target pixel) to be determined as to whether or not it is an inner corner point. Call). Then, based on the pixel value (1 or 0) of the target pixel and a predetermined pixel around it, it is determined whether or not the target pixel is an internal angle point by performing a logical operation as described below. To do. FIG. 9 is a diagram showing a combination pattern 91 of the pixel of interest and predetermined pixels around it, which is used for detecting the inner corner point. In FIG. 9, the pixels used for detecting the inner angle point are indicated by the pixel of interest O and predetermined pixels A, B, and C around the pixel of interest O, and combinations thereof are prepared as a total of eight patterns 91. ing. Then, using the pixel values of the pixel of interest O indicated by each pattern 91 and the predetermined pixels A, B, and C around it, the following logical operation is performed.
On =! O & A & B & C
The above formula can be used! Indicates inversion, and & indicates logical product. 1 indicates that there is a pixel, and 0 indicates that there is no pixel. Then, the above calculation is performed for all the patterns 91 shown in FIG. 9, and if any one of them is On = 1, it is assumed that the pixel of interest P is an inner angle point. Then, by performing such a logical operation while sequentially setting all the pixels of the master image 28 as the target pixel, an inner angle point in the master image 28 is detected.

  If the internal angle point can be detected, the expansion unit 25 then expands (expands) the internal angle point by a predetermined number of steps in the vicinity of 8 (step S13). This is performed for each of all detected interior angle points. Here, the description will be continued on the assumption that the number of stages of 8-near expansion is one stage.

  Subsequently, the expansion unit 25 determines the internal angle point expanded in the vicinity of 8 as an internal angle region, and saves it in the storage unit 26 as an internal angle region image 29 as shown in FIG. 3B (step S14). Since the inner angle area image 29 is for indicating the position of the inner angle in the master image 28, the image size preferably matches the size of the master image 28 (this applies to the outer angle area image 30 described later). Is the same). Thus, the inner corner area image generation process ends. In the generated inner corner area image 29 (FIG. 3B), an area having a pixel value of 1 indicates an inner corner area, and a region of 0 indicates that the area is not an inner corner area. In other words, the interior corner area image 29 is an image that represents whether or not the interior corner area is a binary value. In addition, since the expansion is performed in the vicinity, the inner angle region is a region close to a circle. Thereby, it is possible to universally cope with any shape of the corner formed in various shapes depending on the etching factor.

Next to or in parallel with the inner angle area image generation process, the outer angle area image generation process is performed. FIG. 10 is a flowchart showing details of the outer corner area image generation processing shown in step S2. In FIG. 10, the control unit 21 first causes the corner detection unit 24 to read the master image 28 generated in advance and stored in the storage unit 26 (step S21). Subsequently, the corner detection unit 24 detects the outer corner point from the read master image 28 (step S22). The processing in step S22 will be described more specifically. First, the corner detection unit 24 determines the pixel of interest from each pixel of the master image 28. Then, using the pixel values of the pixel of interest O indicated by each pattern 91 shown in FIG. 9 and the predetermined pixels A, B, and C around it, the following logical operation is performed.
Og = O &! A &! B &! C
Then, the above calculation is performed on all the patterns 91 shown in FIG. 9, and if any one of them is Og = 1, it is determined that the target pixel O is an outside angle point. Then, an outside angle point in the master image 28 is detected by performing such a logical operation while sequentially setting all the pixels of the master image 28 as the target pixel.

  If the outside angle point can be detected, the expansion unit 25 then expands (enlarges) the outside angle point by a predetermined number of steps by 8 (step S23). This is performed for each of the detected outside angle points. Here, it is assumed that the number of stages of 8-neighbor expansion is one, as in step S12.

  Subsequently, the expansion unit 25 determines the outside angle point expanded in the vicinity of 8 as an outside angle region, and saves it in the storage unit 26 as the outside angle region image 30 as shown in FIG. 3C (step S24). The outer corner area image generation process is thus completed. In the outer angle region image 30 (FIG. 3C) generated as a result, a region with a pixel value of 1 indicates an outer angle region, and a region of 0 indicates a region that is not an outer angle region. In other words, the outer corner area image 30 is an image that represents whether or not the outer corner area is a binary angle.

  After the inner corner area image 29 and the outer corner area image 30 are generated by the preparation process as described above, the imaging camera 15 captures an image including the print pattern to be inspected. Then, after the object image 27 obtained by binarizing the captured image is generated by the object image generation unit 22, a comparison inspection process for comparing the object image 27 and the master image 28 is performed. Before explaining the details of this process, an outline of the process will be described with reference to FIG.

  In this process, when the object image 27 and the master image 28 are compared, as shown in FIG. 11A, both the images are divided into blocks of a predetermined size, and the two images are compared and inspected in units of these blocks. To do. In the processing in the block unit, for example, a window called “inspection window” of 5 × 5 pixels as shown in FIGS. 11B and 11C is scanned sequentially from the upper left of the block. Then, the pixels in this inspection window are compared and the difference is taken. If the difference value exceeds a preset allowable value, it is determined that the block is defective at that time.

  Next, details of the comparison inspection process performed by the inspection apparatus 1 will be described. FIG. 12 is a flowchart showing details of the comparison inspection process performed by the inspection apparatus 1. In FIG. 12, the control unit 21 first causes the comparison inspection unit 31 to read the object image 27, the master image 28, the inner corner region image 29, and the outer corner region image 30 (step S31). Next, each read image is subdivided into blocks of a predetermined size (step S32; see FIG. 11). The process of step S32 will be described more specifically. First, the comparative inspection unit 31 determines coordinates that serve as reference points for each image. For example, the comparison inspection unit 31 uses the coordinates (0, 0) of the upper left corner of each image as a reference point. Then, alignment is performed by aligning the reference points of the object image 27, the master image 28, the inner corner area image 29, and the outer corner area image 30 (that is, the upper left corner of each image is aligned). Then, the image is subdivided into blocks of a predetermined size as shown in FIG. 11A from the reference point toward the lower right direction (more precisely, the coordinates serving as the boundaries of the blocks) The value is stored in the storage unit 26). Here, as shown in FIG. 11A, each image is divided into 6 × 6 blocks. Although not shown, the inner corner area image 29 and the outer corner area image 30 are similarly subdivided into 6 × 6 blocks. The size of one block is, for example, 320 × 256 pixels.

  Next, the control unit 21 sets a variable n, which is a variable for identifying each block, to 1 (step S33). In the present embodiment, since each image is subdivided into 6 × 6 blocks, the variable n takes a value within the range of 1 to 36. That is, the variable n indicates the number of the subdivided block. Taking FIG. 11A as an example, the upper left block becomes the first block (n = 1), increases to the right with n = 2, 3,..., And the lower right corner block is n. = 36 blocks.

  Next, a block inspection process is performed for the nth block, in which a comparison inspection between the object image 27 and the master image 28 is performed (step S34). FIG. 13 is a flowchart showing details of the block inspection process shown in step S34.

  In FIG. 13, first, the sway reference position Δ for performing “sway process” is set to the coordinates (0, 0) (step S41).

  Here, the “smooth process” will be described. Generally, since a printed circuit board is composed of a thin plate member, “warping” may occur. Therefore, a subtle “distortion” is also generated in the print pattern formed on the printed circuit board to be inspected. When such “distortion” exists, even if the positions of the master image and the object image are aligned at the same reference point as described above, there may be a portion that is slightly shifted due to “distortion”. . In consideration of such a situation, when the object image 27 and the master image 28 are compared and inspected with the block unit image, the master image size of the nth block is slightly smaller than the object image of the same nth block. A large size is set, and a master image 28 in a range slightly wider than the object image 27 is cut out and compared.

  Specifically, using FIG. 14, for example, an image of 320 × 256 pixels (FIG. 14A) is cut out as one block from the object image 27. On the other hand, for example, an image of 330 × 266 pixels (FIG. 14B), which is larger by 5 pixels each in the vertical and horizontal directions, for example, by 10 pixels in each of the vertical and horizontal directions, is taken as one block from the master image 28. cut. Then, the extracted object image 27 is superimposed on the master image 28 after being cut out, and a comparison inspection is performed with respect to the difference of 10 pixels while shifting the pixel image by 1 pixel (in this way, “moving the image little by little”) Called).

  FIG. 15 is a diagram schematically showing the “smooth process”. As described above, when “distortion” is present in the object image 27, the master image 28 and the object image 27 do not completely coincide with each other only by the alignment in step S <b> 32, and a slight shift occurs. Therefore, by comparing the object image 27 while shifting the object image 27 in the slightly larger master image 28, the subtle deviation between the two is filled. Then, the object images 27 are compared and inspected while shifting, and if the difference value between the two is within the allowable value even once, “no defect” is indicated. If the difference value is not within the allowable value, “defective” is indicated. Judgment.

  The reference position Δ is for determining the position of the object image 27 with respect to the master image 28. In FIG. 15, first, the comparative inspection unit 31 performs a comparative inspection with the reference position Δ = (0, 0) (FIG. 15A). At this point, since the two images do not match at all, the difference value between the two exceeds the allowable value, and as a result, it is determined that there is a defect. Next, a comparative inspection is performed at the position of the reference position Δ = (1, 0) where the object image 27 is moved by +1 in the X direction (FIG. 15B). At this point in time, both images do not match, so it is determined that there is a defect. In this way, the object image 27 is compared while being shifted within the size range of the master image 28. As a result, when the reference position Δ = (1, 1), as shown in FIG. 15C, when the positions of the two images substantially coincide with each other, the difference value between them falls within the allowable value. For this reason, the block is determined to be “no defect” (note that once it is determined that there is no defect, the inspection of the block ends there).

  Returning to FIG. 13, after step S41, the comparison inspection unit 31 cuts out the image of the n-th block from the object image 27, the master image 28, the inner corner region image 29, and the outer corner region image 30, respectively (step S42). ). The processing in step S42 will be described more specifically. First, the comparison inspection unit 31 cuts out an image of the nth block from the object image 27. Hereinafter, the image is referred to as data D. The image size of the data D is the same as the above-described block size, for example, 320 × 256 pixels. Subsequently, the comparison inspection unit 31 cuts out an image of the nth block from the master image 28, the inner corner area image 29, and the outer corner area image 30. Hereinafter, an image cut out from the master image 28 is referred to as data M, an image cut out from the inner corner area image 29 is referred to as data A, and an image cut out from the outer corner area image 30 is referred to as data B. The image sizes of these data M, A, and B are cut out in a size of, for example, 330 × 266 pixels, which is increased by 5 pixels in each of the four directions of the upper, lower, left, and right sides of the block in order to perform the above-described “smooth”.

  Next, the comparison inspection unit 31 sets the difference amount SA between the object image 27 and the master image 28 to zero. In addition, a variable P1 indicating the position of a pixel to be inspected (hereinafter referred to as an inspection point) within the inspection window described with reference to FIG. 11C is set to (0, 0). Further, the variable P2 taking into account the shift amount of the data D (object image 27) by the above-mentioned “smooth process” is set to (0, 0) (step S43). Subsequently, the comparative inspection unit 31 performs window inspection processing for inspecting the image such as the data D using the inspection window (step S44).

  FIG. 16 is a flowchart showing details of the window inspection process shown in step S44. In this process, each pixel (5 × 5 = 25 pixels) in the “inspection window” is comparatively inspected in order. First, the comparison inspection unit 31 acquires a pixel to be inspected (step S61). Specifically, the inspection window is set to the data D (initially, the position is aligned with the upper left corner as a reference), and the pixel value of the coordinates of the data D corresponding to the coordinates in the inspection window indicated by the variable P1 is acquired. . In addition, the inspection window is set to data M, data A, and data B (initially, the position is aligned with the upper left corner as a reference), and the coordinate obtained by adding the reference position Δ to the coordinates in the inspection window indicated by the variable P1 The pixel values (0 or 1) of the coordinates on the data M, data A, and data B corresponding to (coordinate indicated by the variable P2) are respectively acquired. Hereinafter, the pixel value acquired from the data M is the pixel value [m], the pixel value acquired from the data A is the pixel value [a], the pixel value acquired from the data B is the pixel value [b], and the pixel is acquired from the data D. The value is called a pixel value [d].

Next, the comparison inspection unit 31 performs the following logical operation on the pixel value acquired in step S61 (step S62).
S = (! M & d &! A) # (m &! D &! B) (1)
In the above formula (1),! Indicates inversion, & indicates logical product, and # indicates logical sum. Also, the calculation priority is “! → & → # → =” in descending order. Further, S = 1 indicates a difference, and S = 0 indicates no difference.

  The logical operation will be supplementarily described with reference to FIG. FIG. 17 is a diagram for explaining an example of the comparative inspection of the outer angle (star) portion of FIG. In FIG. 17, the reference position Δ = (0, 0), and the inspection point is the position of the variable P1 = (2, 2) (that is, the pixel at the position of the third row and third column). The pixel of the data M (master image 28) corresponding to the inspection point is 1 (with pixels), but the pixel of the data D (object image 27) is 0 (no pixels). In such a case, if only the comparison between the data M and the data D is performed, it is determined that the two do not match (there is a difference). However, according to the present embodiment, since the data B (outer corner area image 30) is 1 (with pixels), it is determined that there is no difference. That is, the inner corner area image 29 and the outer corner area image 30 are used in combination, and the determination criterion is changed according to the area indicated by them.

  In the case of FIG. 17, at the positions of the variable P1 = (2, 2) and the variable P2 = (2, 2), the pixel value [m] = 1, the pixel value [a] = 0, and the pixel value [b] = 1. Pixel value [d] = 0. When these values are used to calculate using the above-described equation (1), it is determined that S = 0, that is, there is no difference. In FIG. 17, the pixel at the lower right of the inspection point (that is, the pixel at the position of the variable P1 = (3, 3) and the variable P2 = (3, 3) and at the position of the fourth row and the fourth column). , Pixel value [m] = 1, pixel value [a] = 0, pixel value [b] = 1, pixel value [d] = 1, and S = 0. Also, the pixel value of the upper left pixel of the inspection point (that is, the pixel at the position of the variable P1 = (1,1) and the variable P2 = (1,1) and at the position of the second row and the second column)) [M] = 0, pixel value [a] = 0, pixel value [b] = 1, pixel value [d] = 0, and S = 0 as a result of the logical operation.

  On the other hand, assume that the pixel value [d] = 1 at the position of the variable P1 = (1, 1) in the data D (object image) of FIG. That is, it is assumed that the outer corner is under-etched and should be detected as a defect. In this case, at the position of variable P1 = (1,1) and variable P2 = (1,1), pixel value [m] = 0, pixel value [a] = 0, pixel value [b] = 1, pixel The value [d] = 1. As a result, it is determined by the logical operation that S = 1, that is, there is a difference. Further, it is assumed that the pixel value [d] = 0 at the position of the variable P1 = (4, 4) in the data D (object image) of FIG. That is, it is assumed that the over-etching at the outer corner has exceeded the allowable range and should be detected as a defect. In this case, at the position of variable P1 = (4, 4) and variable P2 = (4, 4), pixel value [m] = 1, pixel value [a] = 0, pixel value [b] = 0, pixel The value [d] = 0. As a result, it is determined by the logical operation that S = 1, that is, there is a difference. That is, what should be originally detected as a defect, such as over-etching or under-etching exceeding the allowable value, is detected.

  As described above, as for the portion where there is a difference between the master image 28 and the object image 27, as shown in the table of FIG. 5, the combination of the pixel values 0 and 1 of the master image 28 and the object image 27, By using the image 29 and the outer corner area image 30, it is possible to prevent a difference from being taken depending on the state of the inner corner under-etching or the outer corner over-etching. As a result, it is possible to reduce false information about places that are not desired to be detected as defects. In addition, as for the allowable value for the presence / absence determination of the difference, it is necessary to perform inspection by setting a high value around the inner corner portion and the outer corner portion so as not to be determined as a defect even if the difference value is relatively large. Nor. Therefore, it is possible to perform a high-precision comparative inspection in which under-etching and over-etching within an allowable range are not detected as defects while increasing the sensitivity of the comparative inspection.

  Returning to FIG. 16, after the process of step S <b> 62, the comparative inspection unit 31 determines whether or not the calculation result S of the formula (1) is 1 (step S <b> 63). As a result, if S = 1, that is, if there is a difference (YES in step S63), 1 is added to SA (step S64), and the process proceeds to the next step S65. On the other hand, if S = 0 (NO in step S63), the process directly proceeds to step S65.

  Next, the comparative inspection unit 31 moves the inspection point in the inspection window (step S65). That is, a predetermined value is added to the variable P1. For example, when it is desired to move the inspection point to the right by one pixel, (+1, 0) is added to the variable P1. Also, (+1, 0) is added to the variable P2.

  Next, the comparison inspection unit 31 determines whether or not the comparison inspection by the logical operation has been performed on all the pixels in the inspection window (step S66). Specifically, since the inspection window is 5 × 5 pixels, it is determined whether the inspection point has been moved 25 times or more. As a result, if all the pixels in the inspection window have not been inspected (NO in step S66), the comparative inspection unit 31 returns to step S61 and repeats the process. On the other hand, when all the pixels have been inspected (YES in step S66), the comparative inspection unit 31 ends the window inspection process.

  Returning to FIG. 13, next, the comparison inspection unit 31 determines whether or not the difference amount SA exceeds a predetermined allowable value specified in advance (step S <b> 45). That is, it is determined whether or not the difference detected in the inspection window exceeds the allowable value. As a result, when the allowable value is not exceeded (NO in step S45), the comparative inspection unit 31 moves the inspection window by one pixel (step S46). The moving direction is initially assumed to be at the upper left end in the block, and from there, it is moved one pixel at a time in the right direction. When the inspection window comes to the right end of the block, the inspection window is moved down by one pixel, and this time, it is moved in the left direction. When the inspection window comes to the left end, it moves down by one pixel and moves to the right. This movement is repeated until the inspection window goes to the lower right corner.

  Subsequently, the comparison inspection unit 31 determines whether or not the inspection window has moved to all the areas in the block, that is, whether or not all the areas in the block have been inspected (step S47). As a result, if the entire block has not yet been inspected, the comparison inspection unit 31 returns to step S43 and repeats the process. On the other hand, when all the areas in the block are inspected, the comparison inspection unit 31 determines that the nth block has no defect, and stores the inspection result of the nth block in the storage unit 26 as “no defect”. (Step S48), the block inspection process is terminated.

  On the other hand, if the difference SA exceeds the allowable value as a result of the determination in step S45 (YES in step S45), the position of the data D (the object image of the nth block) is set as the master image as described above. In order to perform the “jussling process” in which the “swing” is performed again and the comparative inspection is performed again, the comparative inspection unit 31 adds a predetermined value to the reference position Δ (step S39). This predetermined value is such a value that the data D circulates over the data M. For example, as in the above-described inspection window, a value such as moving from the upper left to the lower right may be added, or first, Δ is set to the center of the data M, and (+1, 0), then (0, +1), next (-1, 0), then (0, -1), and so on, values that move the data D in a spiral shape may be added. .

  Next, as a result of adding a predetermined value to Δ, the comparison inspection unit 31 determines whether or not the position of the data D (for example, one end of the four corners) is out of the range of the size of the data M (330 × 266 pixels). Determination is made (step S50). As a result, if it is out of range (YES in step S50), it means that there was no position where there was no defect (position where both images coincided) as a result of swaying. Therefore, the comparison inspection unit 31 determines that the block has a defect, and stores it in the storage unit 26 as the inspection result of the nth block (step S51). This is the end of the block inspection process.

  Returning to FIG. 12, when the block inspection process is completed, the comparison inspection unit 31 adds 1 to n in order to inspect the next block (step S35). Subsequently, the comparison inspection unit 31 determines whether or not all blocks have been inspected (step S36). As a result, when there remains a block that has not been inspected yet (NO in step S36), the control unit 21 returns to step S34 and repeats the process. On the other hand, when all the blocks have been inspected (YES in step S36), the comparison inspection unit 31 ends the comparison inspection process. The comparison inspection process according to the present embodiment is thus completed.

  As described above, in the present embodiment, when the object image and the master image 28 are compared and inspected, a difference determination criterion is changed depending on whether the difference is an outside angle or an inside angle. . That is, a difference is not taken for over-etching at the outer corner, but a difference is taken for under-etching. Further, a difference is taken for over-etching at the inner corner, but no difference is taken for under-etching. Therefore, it is possible to exclude only a difference that is not desired to be determined as a defect at a corner or corner where there is a difference between the object image 27 and the master image 28. Thereby, a comparative inspection with high accuracy becomes possible. Further, unlike the prior art, there is no need to process the master image 28 such as fleshing the inner corner or dropping the outer corner. Therefore, it is not necessary to provide a circuit for processing the master image 28, and the cost can be reduced by reducing the circuit scale. Also, it is not necessary to prepare two types of tolerance values for the difference determination, that is, tolerance values for the inner and outer corner portions and tolerance values for the other portions as in the prior art. For this reason, only one circuit is required for determining the allowable value, and the circuit scale can be reduced to reduce the cost. In addition, since there is no false information about the inner angle and outer angle (determining overetching etc. as a defect) as in the prior art, and the allowable value can be set lower (that is, the inspection accuracy is increased), more reliable. High comparative inspection is possible. Therefore, it is possible to detect a pattern defect that has been overlooked by reducing the inspection accuracy. Further, in the present embodiment, an area having a shape close to a circle is created by expanding the inner angle or the outer angle in the vicinity. As a result, for example, compared to a method in which a square area pattern is prepared in advance and uniformly applied as an inner corner / outer corner area, any shape of corners and corners formed in various shapes depending on the etching factor can be handled universally. .

  In the above-described embodiment, in the corner detection process (step S12 in FIG. 8 and step S22 in FIG. 10) in the preparation process, the inner angle or the outer angle is detected using the eight patterns 91 as shown in FIG. It was. Not limited to this, more patterns may be used. For example, the detection using the eight patterns 91 described above is “low sensitivity detection”. In contrast, detection using 16 patterns 92 as shown in FIG. 18 is “medium sensitivity detection”. Further, detection using 24 patterns 93 as shown in FIG. 19 is “high sensitivity detection”. In any case, as described above, the pixel values of the pixel of interest O in the pattern 92 or 93 and the predetermined pixels A, B, and C around it (the peripheral predetermined pixel D is also used in the pattern 93) are used. Thus, the logical operation as in steps S12 and S22 described above is performed.

  These “medium sensitivity detection” and “high sensitivity detection” may be used in the following cases. For example, since a straight line pattern formed obliquely as shown in FIG. 20A is expanded when the master image 28 is generated from CAD data, one pattern as shown in FIG. There may be a step in the part. That is, even if it is actually a straight line, a step may be formed by image processing on the master image 28. Such a stepped portion is different from the object image 27 when the inspection accuracy is increased, but is not a defect. However, such a level difference cannot be detected as a corner or a corner in “low sensitivity detection”, and may be determined as a defect. For this reason, a small step (for example, a location where sufficient inspection cannot be performed with “low sensitivity detection” or a location where false detection is possible with “low sensitivity detection”) is appropriately selected as “medium sensitivity detection”. Or “high sensitivity detection” is used to set the inner angle region or the outer angle region. As a result, even a minute step generated in the oblique line as described above can be detected as an “inner angle” or “outer angle”. As a result, the defect criterion can be changed even for a minute step and is not determined as a defect. Therefore, it is not necessary to increase the allowable value, and highly accurate comparative inspection is possible.

  Furthermore, the step number of the 8-neighbor expansion in step S13 or step S13 may be changed in accordance with the width of the linear portion of the print pattern that is close to the inner angle or the outer angle detected by the angle detection unit 24. For example, information on the width of the straight line portion may be acquired in advance from CAD data, and the number of expanding stages may be reduced when the width is narrow, and the number of expanding stages may be determined when it is thick. Needless to say, not only the 8-neighbor expansion but also the 4-neighbor expansion may be used, or the two may be used in combination.

  In step S32, when the object image 27 or the like is divided into blocks, one block range may be divided so as to overlap another block range. For example, when the size of one block is set to 320 × 256 as described above, the coordinates (0, 0) on the left end are changed to the coordinates (0, 0) of the master image 28 or the like for the position of the first block. However, the position of the second block is adjusted to (300, 0) of the master image 28 or the like. In this way, by performing the comparative inspection in units of blocks so that a part of the blocks overlap, it is possible to accurately inspect the pattern at the end of the block. As a result, a more accurate comparative inspection can be performed by using together with the above-mentioned “jussling”.

  Further, regarding the inspection object, in the above-described embodiment, the printed wiring board is the inspection object. However, the present invention is not limited to this, and a semiconductor wafer, a liquid crystal substrate, etc., and a mask film or a printing plate for producing them may be used as the inspection object.

  In the above-described embodiment, the comparative inspection is performed using the binarized images such as the object image 27 and the master image 28. The comparative inspection may be performed using not only such a binarized image but also an image composed of two or more values.

  The difference comparison inspection method and the difference comparison inspection apparatus according to the present invention can perform an appropriate comparison inspection on a pattern formed on a substrate, and are useful for applications such as a substrate inspection apparatus.

The figure which shows typically the whole structure of the optical inspection apparatus which concerns on embodiment of this invention. Functional block diagram showing an optical inspection device according to an embodiment of the present invention The figure which shows an example of the master image 28 The figure which shows an example of the object image 27 The figure which shows the principle of the comparison inspection in this embodiment Flow chart showing details of preparation process Illustration for explaining inner and outer angles The flowchart which shows the detail of an internal corner area | region image generation process shown by step S1 of FIG. The figure which shows the combination pattern of an attention pixel and the predetermined pixel of the circumference for a corner detection The flowchart which shows the detail of an outer corner area | region image generation process shown by step S2 of FIG. The figure which shows an example of the subdivision by the block of an image Flow chart showing details of comparison inspection process The flowchart which shows the detail of the block test | inspection process shown by step S34 of FIG. Illustration for explaining "Yusurase" Illustration for explaining "Yusurase" The flowchart which shows the detail of the window test | inspection process shown by step S44 of FIG. The figure for demonstrating the comparative test | inspection in this embodiment Diagram showing an example of medium sensitivity angle detection pattern The figure which shows an example of a highly sensitive corner detection pattern The figure for explaining the step of the diagonal line Diagram for explaining the conventional comparative inspection method Diagram showing an example of over-etching and under-etching

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical appearance inspection apparatus 11 Stage part 12 Stage support part 13 Stage drive mechanism 14 Base part 15 Imaging camera 16 Support member 17 Camera support part 18 Camera drive mechanism 21 Control part 22 Object image generation part 23 Corner area image generation part 24 Corner Detection unit 25 Expansion unit 26 Storage unit 27 Object image 28 Master image 29 Inner corner region image 30 Outer corner region image 31 Comparative inspection unit

Claims (8)

A difference comparison inspection method for inspecting the inspection object by comparing the object image obtained by imaging the inspection object on which the pattern is formed with the master image of the pattern,
An angle detection step of detecting an inner angle that is a concave corner formed in the pattern and an outer angle that is a convex corner from the master image, respectively.
An inner angle area determining step for determining a range of an inner angle area that is an area in the vicinity of the detected inner angle;
An outer angle region determining step for determining a range of an outer angle region which is a region in the vicinity of the detected outer angle;
A comparison inspection step of performing a comparison inspection based on a difference between the master image and the object image;
The comparative inspection step includes
In the inner angle area of the master image, a comparison inspection is performed by excluding a difference with respect to the pattern area of the object image formed in excess of the pattern area indicated by the master image,
A difference comparison inspection method in which, in the outer angle area of the master image, a comparison inspection is performed by excluding a difference from the pattern area of the object image that is formed less than the pattern area indicated by the master image. Each of the object image and the master image is binarized with a pixel value of a region where the pattern is formed as a first value and other pixel values as a second value different from the first value. Images
The inner angle area determining step further includes an inner angle area image generating step of generating an inner angle area image in which the pixel value in the inner angle area is the first value and the pixel value outside the inner angle area is the second value. ,
The outer angle area determining step further includes an outer angle area image generating step of generating an outer angle area image in which the pixel value in the outer angle area is the first value and the pixel value outside the outer angle area is the second value. The comparative inspection step includes
An alignment step of aligning the master image, the inner angle area image, the outer angle area image, and the object image on the same coordinate axis;
A pixel value acquisition step of acquiring, from each image, a pixel value of a pixel at an inspection target position that is the same position on the coordinate axis;
The pixel value of the acquired object image is the first value, the pixel value of the acquired master image is the second value, and the pixel value of the acquired inner corner area image is the first value. When it is a value, the pixel value of the master image and the object image at the inspection target position is compared and inspected as the same value,
The pixel value of the acquired object image is the second value, the pixel value of the acquired master image is the first value, and the pixel value of the acquired outside angle area image is the first value. The difference comparison inspection method according to claim 1, further comprising a pixel value determination step of comparing and inspecting the pixel value of the master image and the object image at the inspection target position as the same value when the value is a value. The corner detecting step detects one pixel indicating the inner angle or the outer angle from the master image,
In the inner angle area determining step, an area having a predetermined size centered on the pixel that is the detected inner angle is determined as the inner angle area,
The comparative inspection method according to claim 1, wherein in the outer angle area determination step, an area having a predetermined size centered on the pixel having the detected outer angle is determined as the outer angle area. In the inner angle region determining step, the inner angle region is determined by repeatedly performing expansion processing for a predetermined number of times for the detected inner angle pixels,
The difference comparison inspection method according to claim 3, wherein the outer-angle region determining step determines the outer-angle region by repeatedly performing expansion processing on the detected outer-angle pixels by a predetermined number of times or more. . And a width detecting step for detecting a width of the linear portion of the pattern close to the detected inner angle or outer angle,
The inner corner area image generation step changes the number of times the expansion process is repeated according to the detected width,
The comparative inspection method according to claim 4, wherein in the outer corner region image generation step, the number of times the expansion process is repeated is changed according to the detected width. The corner detection step includes a pixel value extracted from the master image using a plurality of patterns respectively indicating a pixel value of the target pixel in the master image and positions of the plurality of pixels extracted based on the target pixel; And a logical operation step of detecting that the pixel of interest is one pixel indicating the inner angle or the outer angle using the logical expression of
In the logical operation step, an operation result of the predetermined logical expression in which a pixel value extracted using any one of the patterns and a pixel value of the target pixel is substituted is an internal angle or an external angle. The comparison inspection method according to claim 3, wherein the target pixel is detected as one pixel indicating the inner angle or the outer angle. The corner detection step uses a pixel value of the target pixel in the master image and a pixel value extracted from the master image using a plurality of patterns respectively indicating positions of a plurality of pixels extracted based on the target pixel. A logical operation step of detecting that the target pixel is one pixel indicating the inner angle or the outer angle;
The logical operation step includes
When the pixel value of the target pixel indicates the area of the pattern indicated by the master image, and the pixel value of the target pixel is different from all the pixel values extracted using any one of the patterns, the target pixel Is detected as one pixel indicating the outer angle,
When the pixel value of the target pixel indicates outside the area of the pattern indicated by the master image, and the pixel value of the target pixel is different from all the pixel values extracted using any one of the patterns, the target pixel The comparison inspection method according to claim 3, wherein the pixel is detected as one pixel indicating the inner angle. A differential comparison inspection apparatus that inspects the inspection object by comparing the object image obtained by imaging the inspection object on which the pattern is formed with the master image of the pattern,
An angle detection unit that detects an inner angle that is a concave corner and an outer angle that is a convex corner formed in the pattern, respectively, from the master image;
An internal angle region determination unit that determines a range of an internal angle region that is a region in the vicinity of the detected internal angle;
An outside angle region determining unit that determines a range of an outside angle region that is a region in the vicinity of the detected outside angle;
A comparison inspection unit that performs a comparison inspection based on a difference between the master image and the object image;
The comparison inspection unit
In the inner angle area of the master image, a comparison inspection is performed by excluding a difference with respect to the pattern area of the object image formed in excess of the pattern area indicated by the master image,
A difference comparison inspection apparatus that excludes a difference from the pattern area of the object image that is formed in the outer angle area of the master image and is less than the pattern area indicated by the master image, and performs a comparison inspection.

Images