JP2018155600A - Visual inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visual inspection apparatus capable of suppressing erroneous detection of defects. An visual inspection device 100 includes an imaging unit 40 that images a plurality of cells 220 having a repeating pattern, an inspection unit 51 that determines whether the cells 220 are non-defective or not, and a plurality of imaged cells. An image adjusting unit 52 that enlarges or reduces the images of the plurality of captured cells 220 so that the pitch of the pattern in the image of the cells 220 is approximately an integral multiple of the pixel resolution of the inspection unit 51 is provided. Then, the inspection unit 51 groups the patterns straddling the plurality of adjacent cells 220 in the enlarged or reduced image of the plurality of cells 220, and combines the grouped patterns into the unit area of the pixel resolution of the inspection unit 51. It is configured to determine whether or not the cell 220 is a non-defective product by comparing each A. [Selection diagram] Fig. 5

Description

  The present invention relates to an appearance inspection apparatus, and more particularly to an appearance inspection apparatus including an inspection unit that determines whether a cell is a non-defective product.

  Conventionally, an appearance inspection apparatus including an inspection unit that determines whether or not a cell is a non-defective product is known (see, for example, Patent Document 1).

  Patent Document 1 discloses an appearance inspection apparatus that detects defects by comparison inspection between repeated patterns using the repeatability of patterns on a semiconductor wafer. This appearance inspection apparatus includes a microscope unit that images a semiconductor wafer. A plurality of chips are arranged on a semiconductor wafer that is an inspection object. Each chip has a plurality of memory cells arranged in a matrix. Then, the appearance inspection apparatus detects a defect in the memory cell by comparing the image of a certain memory cell with the image of another memory cell in the image captured by the microscope unit. Note that a repetition period (interval between memory cells, etc.) of patterns of a plurality of memory cells arranged in a matrix is input in advance to the appearance inspection apparatus. The appearance inspection apparatus is configured to perform a comparison (cell to cell inspection) between memory cells based on a repetition period (repeatability) of a pattern input in advance. Specifically, the brightness value of an image in a predetermined area of one memory cell (pattern) is compared with the brightness value of an image in a predetermined area of another memory cell. If there is a difference in the compared luminance values, it is determined that a defect has occurred in one memory cell (or another memory cell).

JP 2001-189358 A

  Here, in the conventional visual inspection apparatus as described in Patent Document 1, the microscope unit that captures an image of a cell has pixel resolution (imaging size per pixel). In the appearance inspection apparatus, the inspection is performed while comparing the luminance value for each rectangular unit region (hereinafter referred to as a unit region of pixel resolution) whose one side is the length corresponding to the pixel resolution.

  For example, when comparing the luminance of one end of one memory cell with the luminance of one end of another memory cell, a unit region (hereinafter, referred to as a pixel resolution) at one end (boundary) of one memory cell. The luminance of one end of one memory cell is acquired in a state where the end (boundary) of the unit region 1) is matched. However, when the luminance of one end of another memory cell is acquired, a unit region (hereinafter referred to as unit region 2) having a pixel resolution may straddle one end of the other memory cell. That is, in the unit region 1, the luminance of only one end of one memory cell is acquired, while in the unit region 2, the luminance of one end of another memory cell and one end of another memory cell are adjacent. And the brightness of another memory cell to be acquired. For this reason, the luminance at one end of one memory cell may not be appropriately compared with the luminance at one end of another memory cell. As a result, it is determined that a defect has actually occurred even if one end of one memory cell and one end of another memory cell are not defective (non-defective). (Defects are mistakenly detected).

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an appearance inspection apparatus capable of suppressing erroneous detection of defects.

  In order to achieve the above object, an appearance inspection apparatus according to one aspect of the present invention includes an imaging unit that images a plurality of cells each having a repetitive pattern, an inspection unit that determines whether a cell is a non-defective product, An image adjustment unit for enlarging or reducing the image of the plurality of captured cells so that the pattern pitch in the captured image of the plurality of cells is approximately an integer multiple of the pixel resolution of the inspection unit. In the image of a plurality of cells that have been enlarged or reduced, the unit collects the patterns spanning a plurality of adjacent cells, and compares the combined patterns for each unit region of the pixel resolution of the inspection unit. It is configured to determine whether or not the cell is a non-defective product.

  In the appearance inspection apparatus according to one aspect of the present invention, as described above, the inspection unit is enlarged or reduced so that the pitch of the pattern in the captured image of the plurality of cells is substantially an integer multiple of the pixel resolution of the inspection unit. In a reduced image of a plurality of cells, a pattern extending over a plurality of adjacent cells is grouped, and the grouped patterns are compared for each unit area of the pixel resolution of the inspection unit to determine whether the cell is non-defective It is configured to determine whether or not. As a result, the images of the plurality of cells are enlarged or reduced so that the pattern pitch is substantially an integer multiple of the pixel resolution of the inspection unit. The boundary of the other pattern and the boundary of the unit area of the pixel resolution coincide with each other. As a result, the luminance value of a predetermined unit region (one end portion or the like) of one pattern that is grouped together is appropriately compared with the luminance value of a predetermined unit region (one end portion or the like) of another pattern. Can do. That is, a predetermined unit region (such as one end) of another pattern does not partially include a unit region of one pattern (a unit region of pixel resolution straddles the boundary between one pattern and another pattern). In this state, the luminance values can be compared. As a result, it is possible to suppress erroneous detection of defects. Here, the unit area of the pixel resolution in the present invention means a rectangular unit area whose one side has a length corresponding to the pixel resolution.

  In addition, when a unit area of one pattern is partially included in a predetermined unit area (one end portion or the like) of another pattern (a unit area of pixel resolution is a boundary between one pattern and another pattern). In order to suppress false detection of defects in a predetermined unit area (one end, etc.) of another pattern, the threshold value of the difference in luminance value for determining that a defect has occurred is increased. It is possible to do. On the other hand, by increasing the threshold value of the difference in luminance value for determining that a defect has occurred, a fine defect is overlooked, so that the detection sensitivity is lowered. Therefore, in the present invention, the difference in luminance value for determining that a defect has occurred by enlarging or reducing the image of a plurality of cells so that the pattern pitch is approximately an integral multiple of the pixel resolution of the inspection unit. Since it is not necessary to increase the threshold value, it is possible to suppress a decrease in detection sensitivity.

  In the appearance inspection apparatus according to the above aspect, the image adjustment unit preferably enlarges the image of the plurality of cells captured at a magnification equal to or lower than a predetermined magnification, or reduces the image at a predetermined reduction. It is configured to reduce the images of a plurality of cells at a reduction rate less than the rate. Here, when the captured images of a plurality of cells are relatively enlarged to exceed a predetermined enlargement ratio, the number of unit areas to be compared increases, and the burden of processing for comparison is increased. growing. In addition, when the captured images of a plurality of cells are reduced to a relatively small size exceeding a predetermined reduction ratio, the image corresponding to the defect is reduced and crushed. That is, the difference between the luminance value of the non-defective pattern (cell) image and the luminance value of the image of the pattern including the defect becomes small, and the defect may not be detected (the defect is overlooked). Therefore, in the present invention, the processing for comparison is performed by enlarging the images of a plurality of cells at an enlargement ratio equal to or lower than a predetermined enlargement ratio, or reducing the images of the plurality of cells at a reduction ratio equal to or lower than a predetermined reduction ratio. It is possible to suppress the oversight of defects while suppressing an increase in the burden of.

  In this case, preferably, the image adjustment unit further includes a determination unit that determines an enlargement rate or a reduction rate of the image of the plurality of cells in advance before the enlargement or reduction of the image of the plurality of cells. While changing the rate or reduction rate, enlarge or reduce the image of the captured non-defective cells, and compare the images of the patterns that are grouped together of the non-defective cells to compare the non-defective cells The enlargement ratio or the reduction ratio is determined so that the difference between the brightness values of the images of the combined patterns becomes substantially zero. With this configuration, even when the enlargement ratio or reduction ratio at which the pattern pitch is approximately an integer multiple of the pixel resolution of the inspection unit is not known, the pattern pitch is approximately an integer multiple of the pixel resolution of the inspection unit. The enlargement ratio or reduction ratio can be easily (automatically) determined.

  In the appearance inspection apparatus according to the above aspect, the inspection unit preferably compares the pattern in which a predetermined number of patterns or less are grouped together for each unit region of the pixel resolution of the inspection unit to determine whether the cell is a non-defective product. It is configured to determine whether or not. Here, when the number of patterns to be collected is relatively large, cells arranged at positions separated by a relatively large distance are compared with each other. For this reason, even if the cells to be compared are non-defective, there may be a difference in the luminance value of the image due to a difference in how the light strikes. Therefore, in the present invention, cells arranged at relatively close positions are compared by grouping a predetermined number of patterns or less, so that an error in a defect caused by a difference in how light strikes or the like is compared. Detection can be suppressed.

  According to the present invention, erroneous detection of defects can be suppressed as described above.

1 is an overall view of an appearance inspection apparatus according to an embodiment of the present invention. It is a figure which shows the several element chip | tip provided in the wafer. It is a figure which shows the image of a some cell. It is a figure which shows the image (before reduction) of a some cell. It is a figure (1) which shows a picture (after reduction) of a plurality of cells. It is a figure (2) which shows a picture (after reduction) of a plurality of cells. It is a figure for demonstrating the method of expansion (reduction | reduction) of an image.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

[This embodiment]
(Structure of appearance inspection equipment)
With reference to FIGS. 1-7, the structure of the external appearance inspection apparatus 100 by this embodiment is demonstrated. The appearance inspection apparatus 100 compares the cells 220 (see FIG. 2) included in the element chips 210 formed on the surface of the semiconductor substrate with each other to determine whether the cells 220 are non-defective (defects, etc.). Whether or not) is determined.

  As shown in FIG. 1, the appearance inspection apparatus 100 includes a moving stage 10. The moving stage 10 includes an X-axis slider 11 and a Y-axis slider 12. The X-axis slider 11 is disposed on the base 20. The Y-axis slider 12 is disposed on the X-axis slider 11.

  In addition, the appearance inspection apparatus 100 includes a placement table 30. The mounting table 30 is disposed on the Y-axis slider 12. The mounting table 30 is configured to be moved in the X direction and the Y direction by the moving stage 10. The mounting table 30 is configured to mount the wafer 200 thereon.

  In addition, the appearance inspection apparatus 100 includes an imaging unit 40. The imaging unit 40 is configured to image the element chip 210 (see FIG. 2). Specifically, the imaging unit 40 is configured to image a plurality of cells 220 (see FIG. 2) provided in a plurality of elements in one element chip 210. The imaging unit 40 includes a lens barrel 41, a half mirror 42, an objective lens 43, and an imaging camera 44. The imaging camera 44 includes a light receiving element 44a.

  Further, as shown in FIG. 3, the element chip 210 is formed with a plurality of cells 220 each having a repeating pattern (a square region surrounded by a thick line in FIG. 3). The plurality of cells 220 are arranged in a matrix. In FIG. 3, only nine cells 220 among the plurality of cells 220 are shown.

  The cell 220 is, for example, a pixel of an imaging device such as a complementary metal oxide semiconductor (COMS) sensor or a charge coupled device (CCD) sensor. 3, one cell 220 (pixel) includes one red (R) subpixel 220a, one blue (B) subpixel 220a, and two green (G) subpixels. 220a. In one cell 220, the red (R) sub-pixel 220a and the green (G) sub-pixel 220a are arranged adjacent to each other in the X direction. Further, the green (G) sub-pixel 220a and the blue (B) sub-pixel 220a are arranged adjacent to each other in the X direction. That is, in a state where the plurality of cells 220 are arranged in a matrix, a repetitive pattern of red (R) sub-pixels 220a and green (G) sub-pixels 220a is formed in the X direction. In addition, a repeating pattern of green (G) sub-pixels 220a and blue (B) sub-pixels 220a is formed in the X direction.

  In addition, as shown in FIG. 1, the appearance inspection apparatus 100 includes an inspection unit 51. The inspection unit 51 is configured to determine whether or not the cell 220 is a non-defective product. The inspection unit 51 (imaging unit 40) has a pixel resolution. The pixel resolution is an imaging size (mm / pixel) per pixel of a CCD (CMOS) sensor. Specifically, as shown in FIGS. 4 and 5, the inspection unit 51 surrounds an image captured by the imaging unit 40 with a square whose side is the pixel resolution length (L, see FIG. 5). The luminance value data of the unit area A (hereinafter referred to as the unit area A with pixel resolution) is acquired.

  In this embodiment, as shown in FIG. 1, the appearance inspection apparatus 100 includes an image adjustment unit 52. As shown in FIG. 5, the image adjustment unit 52 captures the plurality of captured cells 220 such that the pattern pitch in the captured image of the plurality of cells 220 is approximately an integer multiple of the pixel resolution of the inspection unit 51. The image is configured to be enlarged or reduced. In FIG. 5, the image is reduced so that the pitch (P) in the X direction of the pattern is approximately 11 times the pixel resolution (L). Then, in the image of the plurality of cells 220 enlarged or reduced, the inspection unit 51 collects the patterns straddling a plurality of adjacent cells 220 and sets the combined patterns to a unit area of pixel resolution of the inspection unit 51. By comparing each A, it is configured to determine whether or not the cell 220 is a non-defective product. Details of operations (functions) of the image adjustment unit 52 and the inspection unit 51 will be described later.

  In the present embodiment, as shown in FIG. 1, the appearance inspection apparatus 100 preliminarily enlarges or reduces the image of the plurality of cells 220 by the image adjustment unit 52. Or the determination part 53 which determines a reduction rate is provided. Details of the operation (function) of the determination unit 53 will be described later.

  Note that the inspection unit 51, the image adjustment unit 52, and the determination unit 53 are included in the control unit 50 that controls the overall operation of the appearance inspection apparatus 100.

  Next, the Cell to Cell inspection will be described with reference to FIG.

  FIG. 3 illustrates images of nine cells 220 among the images of the plurality of cells 220 captured by the imaging unit 40. Here, it is assumed that the cell 221 arranged at the center of the nine cells 220 is an inspection target. In the Cell to Cell inspection, first, the luminance value of the cell 222 (for example, the sub-pixel 220a (R)) arranged above the cell 221 and the luminance value of the cell 221 (the sub-pixel 220a (R)) Are compared. Next, the luminance value of the cell 223 (subpixel 220a (R)) disposed below the cell 221 is compared with the luminance value of the cell 221 (subpixel 220a (R)). Next, the luminance value of the cell 224 (sub pixel 220a (R)) arranged on the left side of the cell 221 is compared with the luminance value of the cell 221 (sub pixel 220a (R)). Finally, the luminance value of the cell 225 (sub pixel 220a (R)) arranged on the right side of the cell 221 is compared with the luminance value of the cell 221 (sub pixel 220a (R)).

  Here, when a defect occurs in the sub-pixel 220a (R) of the cell 222, the difference between the luminance value of the sub-pixel 220a (R) of the cell 222 and the luminance value of the sub-pixel 220a (R) of the cell 221 is Relatively large (becomes above threshold). On the other hand, the luminance of the sub pixel 220 a (R) of the cell 223, the sub pixel 220 a (R) of the cell 224, the sub pixel 220 a (R) of the cell 225, and the sub pixel 220 a (R) of the cell 221 The difference from the value is relatively small (below the threshold). That is, in the above four comparisons, the luminance value difference is 1 time when the difference is greater than or equal to the threshold value, and the luminance value difference is less than the threshold value 3 times. In this case, based on the majority decision, it is determined that the sub-pixel 220a (R) of the cell 221 is a non-defective product (no defect or the like).

  On the other hand, when the sub-pixel 220a (R) of the cell 222 in which the defect has occurred is the inspection target, and the cells 220 arranged above, below, left, and right of the cell 222 are non-defective, In the comparison, the case where the difference in luminance value is equal to or greater than the threshold value is four times. In this case, based on the majority decision, the sub-pixel 220a (R) of the cell 222 is determined to be defective (has a defect or the like).

  Specifically, as shown in FIGS. 4 and 5, the inspection unit 51 compares the luminance values for each unit area A of pixel resolution. For example, when there is a pattern of red (R) sub-pixels 220a and green (G) sub-pixels 220a in the X direction (left and right in the drawing), the pattern is positioned at the left end of red sub-pixel 220a of cell 221. The luminance value of the unit area A (A11) with pixel resolution to be compared with the luminance value of the unit area A (A21) with pixel resolution located at the left end of the red sub-pixel 220a of the cell 225 adjacent to the right side of the cell 221. Is done. Similarly, the luminance values of the unit areas A12 to A16 are compared with the luminance values of the unit areas A22 to A26, respectively.

  Here, there are cases where the pitch of the pattern and the pixel resolution do not match (the boundary between the patterns and the boundary of the unit area A of the pixel resolution do not match). For example, as shown in FIG. 4, the left end of the red sub-pixel 220a of the cell 221 (the left end of the pattern PT11) coincides with the boundary of the unit area A1 of pixel resolution. On the other hand, the left end of the red sub-pixel 220a of the cell 225 (the left end of the pattern PT12) does not coincide with the boundary of the unit area A (A21) of pixel resolution. Specifically, the unit area A21 of pixel resolution straddles the green sub-pixel 220a of the cell 221 and the red sub-pixel 220a of the cell 225. In this case, the difference between the luminance value of the pixel resolution unit area A11 and the luminance value of the pixel resolution unit area A21 is relatively large. As a result, even if the unit area A11 and the unit area A21 are both non-defective products, it may be determined that a defect or the like is present (a case where a defect is erroneously detected). Hereinafter, the operation of the appearance inspection apparatus 100 of the present embodiment capable of suppressing erroneous detection of defects will be described.

  Next, the operation of the appearance inspection apparatus 100 will be described with reference to FIGS. 4 and 5 show images of three cells 220 arranged along the X direction. FIG. 6 shows an image of six cells 220 arranged along the X direction.

<Image capture>
First, the element chip 210 (see FIG. 2) is imaged by the imaging unit 40. As shown in FIG. 4, the image of the element chip 210 includes images of a plurality of cells 220 each having a repeated pattern.

<Enlarge / reduce image>
Next, as illustrated in FIG. 5, the image adjustment unit 52 captures the plurality of captured images so that the pattern pitch in the captured images of the cells 220 is approximately an integer multiple of the pixel resolution of the inspection unit 51. The image of the cell 220 is enlarged or reduced. For example, the image adjustment unit 52 is configured to enlarge or reduce the image of the plurality of cells 220 at an enlargement rate of 5% or less or a reduction rate of 5% or less. That is, the image is reduced or enlarged to a size of 95% or more and 105% or less with respect to the size of the original image. The enlargement ratio or reduction ratio of the images of the plurality of cells 220 is determined in advance by the determination unit 53 (before inspection). A method of determining the enlargement rate or reduction rate by the determination unit 53 will be described later.

  For example, the width W1 in the X direction of the image of the plurality of cells 220 shown in FIG. 4 is reduced to the width W2 as shown in FIG. Here, in FIG. 4, the unit region A31 of pixel resolution straddles the right end of the green sub-pixel 220a of the cell 225 and the red sub-pixel 220a of the cell 226 adjacent to the right side of the cell 225. On the other hand, as shown in FIG. 5, by reducing the image of the plurality of cells 220 in the X direction, the boundary of the unit region A31 with pixel resolution matches the boundary of the red sub-pixel 220a of the cell 226. That is, the red subpixel 220a and the green subpixel 220a in one cell 220 are regarded as one pattern (patterns PT11 and PT12 in FIG. 4), and the patterns (units of pixel resolution of corresponding portions in the two patterns). When comparing the luminance values of the regions A), the unit region A31 (A21) of pixel resolution straddles one pattern and the other pattern. On the other hand, as shown in FIGS. 5 and 6, the width W <b> 2 in the X direction of the image of the plurality of cells 220 is reduced, and two patterns straddling the plurality of adjacent cells 220 are grouped together. Then, the combined patterns (PT21, PT22) are compared. As a result, the boundary of the pattern PT21 and the boundary of the unit area A11 with pixel resolution match, and the boundary of the pattern PT22 and the boundary of the unit area A31 with pixel resolution match. That is, instead of comparing the cell 221 and the cell 225 adjacent to the cell 221, the cell 221 and the cell 226 on the right side of the cell 225 are compared.

  Further, the unit areas A13, A16 (A21), A24, etc. of the pixel resolution in the pattern PT21 straddle the boundary of the sub-pixel 220a. However, the unit areas corresponding to the unit areas A13, A16 (A21), and A24 of the pixel resolution in the pattern PT22 are also the same as the unit areas A13, A16 (A21), and A24 of the pixel resolution of the pattern PT21. It straddles the boundary. Further, since the luminance values are compared between the boundaries of the sub-pixels 220a (unit areas A that straddle the left and right sub-pixels 220a at the same rate), a defect is not erroneously detected.

  The image adjustment unit 52 enlarges the captured image of the plurality of cells 220 with a relatively small enlargement ratio (or reduces with a relatively small reduction ratio), thereby reducing the pattern pitch to the pixel resolution. An integer multiple is used (the boundary of the pattern and the boundary of the unit area A are matched). Specifically, in FIG. 4, it is conceivable that the boundary of either the unit area A21 or the unit area A31 of pixel resolution is matched with the pattern boundary. In this case, the image width W1 is reduced so that the pattern boundary matches the boundary of the unit area 21 when the pattern width W1 is reduced so that the pattern boundary matches the boundary of the unit area 31. The reduction ratio of the image is smaller than that in the case of doing so. Therefore, the image adjustment unit 52 is configured to reduce the width W1 of the image so that the pattern boundary coincides with the boundary of the unit region 31 so that the reduction ratio is as small as possible.

  Further, in the present embodiment, the inspection unit 51 compares the patterns in which a predetermined number of patterns or less are grouped together for each unit area A of the pixel resolution of the inspection unit 51, thereby determining whether or not the cell 220 is a non-defective product. It is comprised so that discrimination | determination may be performed. That is, the upper limit value of patterns to be collected is determined. In FIG. 5, two adjacent patterns are grouped together. Note that the upper limit value of patterns to be collected is three (three cells 220), for example.

  FIG. 5 shows an example in which the image of the plurality of cells 220 is reduced in the X direction. In the Y direction, the pattern pitch is set to be approximately an integer multiple of the pixel resolution (with the pattern boundary). The image is enlarged or reduced so that the boundary of the unit area A of the pixel resolution coincides). In FIG. 5, the pixel resolution unit areas A are described in one column in the X direction. Actually, however, the pixel resolution unit areas A are arranged in a matrix (two-dimensional) in the X and Y directions. Exists.

  Here, when a new image is formed by enlarging (or reducing) the original image, a method of coordinate conversion of the pixel position in the original image is conceivable. That is, as shown in FIG. 7, it is calculated whether the pixel at one point located at the coordinates in the new coordinate system after coordinate transformation corresponds to the pixel at the current coordinate system (before coordinate transformation), The pixel in the current coordinate system is moved to the new coordinate system pixel. Here, if the coordinates (x, y) of the position of the current coordinate system corresponding to one pixel in the new coordinate system obtained by calculation are integers, the pixel (luminance) is set to the coordinates (x, y). Value) exists. On the other hand, when the coordinates (x, y) obtained by calculation are not integer values, there are no pixels (luminance values) at these coordinates. Therefore, in this embodiment, when the coordinate (x, y) obtained by calculation is not an integer value, the luminance value is linearized according to the distance from four pixels in the vicinity of the coordinate (x, y) obtained by calculation. It is configured to complement. That is, the coordinates (x, y) obtained by calculation and the coordinates (x1, y1), coordinates (x2, y2), coordinates (x3, y3), and coordinates (x The luminance values are linearly complemented by a weighted average corresponding to the distance between each of x4 and y4). For example, when the distance to the coordinates (x2, y2) is relatively small, a relatively large proportion of luminance values are added (complemented) from the luminance values of the pixels corresponding to the coordinates (x2, y2). On the other hand, when the distance to the coordinate (x3, y3) is relatively large, a relatively small ratio of luminance values is added (complemented) to the luminance value of the pixel corresponding to the coordinate (x3, y3).

<Inspection>
Then, the inspection unit 51 determines whether or not the cell 220 is a non-defective product by comparing the combined pattern PT21 and pattern PT22 for each unit area A of pixel resolution (Cell to Cell inspection). Cell to Cell inspection is performed for all cells 220. Whether or not the cell 220 is a non-defective product is determined by a majority vote based on a plurality of comparisons as described above.

<Determination method of enlargement ratio or reduction ratio>
Next, with reference to FIG. 4 and FIG. 5, a method for determining an image enlargement rate or reduction rate by the determination unit 53 will be described. The determination of the image enlargement ratio or reduction ratio by the determination unit 53 is performed in advance before the actual cell 220 inspection.

  As shown in FIG. 4, first, images of a plurality of non-defective cells 220 are prepared (captured). In the present embodiment, the determination unit 53 enlarges or reduces the image of the plurality of captured non-defective cells 220 while changing the enlargement ratio or the reduction ratio. Then, the images of the combined patterns of the non-defective cells 220 are compared. Thereafter, the determination unit 53 determines the enlargement ratio or the reduction ratio so that the difference between the luminance values of the images of the collected patterns of the cells 220 is substantially zero. That is, in the state shown in FIG. 4, the difference in luminance value between the pattern PT11 (unit areas A11 to A16) and the pattern PT12 (unit areas A21 to A26) is relatively large. On the other hand, in the state shown in FIGS. 5 and 6, the difference between the luminance value of the pattern PT21 and the luminance value of the pattern PT22 is substantially zero. That is, when luminance values are compared between non-defective cells 220, the difference in luminance values is essentially zero. On the other hand, as shown in FIG. 4, when the unit region A straddles the boundary of the pattern, the luminance value difference is relatively large even between the non-defective cells 220. Therefore, by determining the enlargement ratio / reduction ratio so that the difference from the luminance value becomes substantially zero, the boundary of the pattern and the boundary of the unit area A can be matched.

  In addition, the determination unit 53 is configured so that the difference between the luminance values of the images of the collected patterns becomes substantially zero within a range where the number of patterns to be collected is a predetermined number (for example, 3) or less. Determine the enlargement or reduction ratio. Thereby, for example, when the image is enlarged (reduced) by a certain enlargement rate (reduction rate), when the four patterns are collected together, the difference in the luminance values of the images of the combined patterns becomes substantially zero. Even in this case, this enlargement rate (reduction rate) is not adopted.

(Effect of this embodiment)
Next, the effect of this embodiment will be described.

  In the present embodiment, as described above, the inspection unit 51 includes a plurality of enlarged or reduced images so that the pattern pitch in the captured image of the plurality of cells 220 is substantially an integer multiple of the pixel resolution of the inspection unit 51. In the image of the cell 220, whether the cell 220 is a non-defective product by grouping the patterns straddling a plurality of adjacent cells 220 and comparing the collected patterns for each unit area A of the pixel resolution of the inspection unit 51. It is configured to determine whether or not. As a result, the images of the plurality of cells 220 are enlarged or reduced so that the pattern pitch is substantially an integer multiple of the pixel resolution of the inspection unit 51. The boundary of the unit area A matches, and the boundary of the other pattern grouped together matches the boundary of the unit area A of pixel resolution. As a result, the luminance value of a predetermined unit area A (one end portion or the like) of one grouped pattern is appropriately compared with the luminance value of a predetermined unit area A (one end portion or the like) of another pattern. can do. That is, a predetermined unit region A (one end portion or the like) of another pattern does not partially include one unit region A (pixel resolution unit region A is a boundary between one pattern and another pattern). The luminance values can be compared with each other in a state in which the image does not straddle. As a result, it is possible to suppress erroneous detection of defects.

  In addition, when a unit area A of one pattern is partially included in a predetermined unit area A (one end portion or the like) of another pattern (the unit area A of pixel resolution is one pattern and another pattern In order to suppress false detection of a defect in a predetermined unit area A (one end portion, etc.) of another pattern, the difference in luminance value for determining that a defect has occurred is measured. It is conceivable to increase the threshold value. On the other hand, by increasing the threshold value of the difference in luminance value for determining that a defect has occurred, a fine defect is overlooked, so that the detection sensitivity is lowered. Therefore, as in the present embodiment, it is determined that a defect has occurred by enlarging or reducing the image of the plurality of cells 220 so that the pattern pitch is substantially an integer multiple of the pixel resolution of the inspection unit 51. Since it is not necessary to increase the threshold value of the difference in luminance value to be detected, it is possible to suppress a decrease in detection sensitivity.

  In the present embodiment, as described above, the image adjustment unit 52 enlarges the captured image of the plurality of cells 220 at an enlargement rate equal to or lower than the predetermined enlargement rate, or The image of the plurality of cells 220 is reduced at a reduction rate equal to or lower than the reduction rate. Here, when the captured images of the plurality of cells 220 are enlarged relatively large exceeding a predetermined enlargement ratio, the number of unit regions A to be compared increases, and the processing for comparison is performed. The burden increases. In addition, when the captured images of the plurality of cells 220 are reduced relatively small exceeding a predetermined reduction ratio, the image corresponding to the defect is reduced and crushed. That is, the difference between the brightness value of the image of the non-defective pattern (cell 220) and the brightness value of the image of the pattern including the defect becomes small, and the defect may not be detected (the defect is overlooked). Therefore, as in the present embodiment, by enlarging the image of the plurality of cells 220 at an enlargement ratio equal to or less than a predetermined enlargement ratio, or reducing the image of the plurality of cells 220 at a reduction ratio equal to or less than the predetermined reduction ratio, It is possible to suppress oversight of defects while suppressing an increase in the burden of processing for comparison.

  Further, in the present embodiment, as described above, the determination unit 53 enlarges or reduces the image of the captured non-defective cells 220 while changing the enlargement ratio or the reduction ratio, and the non-defective cells. 220. Compare the images of the grouped patterns 220, and determine the enlargement ratio or the reduction ratio so that the difference in luminance value between the images of the grouped non-defective cells 220 is substantially zero. To do. Thereby, even when the enlargement ratio or reduction ratio at which the pattern pitch is approximately an integer multiple of the pixel resolution of the inspection unit 51 is not known, the enlargement ratio at which the pattern pitch is an approximately integer multiple of the pixel resolution of the inspection unit 51 Alternatively, the reduction ratio can be easily (automatically) determined.

  Further, in the present embodiment, as described above, the inspection unit 51 compares the patterns in which a predetermined number of patterns or less are grouped together for each unit region A of the pixel resolution of the inspection unit 51, thereby the cell 220. It is configured to determine whether or not the product is a non-defective product. Here, when the number of patterns to be collected is relatively large, the cells 220 arranged at positions separated by a relatively large distance are compared with each other. For this reason, even if the cells 220 to be compared with each other are non-defective, there may be a difference in the luminance value of the image due to a difference in how light strikes. Therefore, as in this embodiment, the cells 220 arranged at relatively close positions are compared by grouping a predetermined number of patterns or less, resulting in a difference in how the light strikes. It is possible to suppress erroneous detection of defects.

[Modification]
The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments and examples but by the scope of claims for patent, and includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above-described embodiment, an example in which the inspection unit inspects a cell including pixels has been described, but the present invention is not limited thereto. For example, the inspection unit may be configured to inspect cells other than pixels, such as memory cells.

  Moreover, although the example which inspects a cell by comparing the pattern by which two patterns were put together was shown in the said embodiment, this invention is not limited to this. For example, the cell may be inspected by comparing patterns obtained by collecting a number of patterns other than two.

  In the above embodiment, an example in which the upper limit of the enlargement ratio is 5% (the upper limit of the reduction ratio is 5%) has been described, but the present invention is not limited to this. In the present invention, the upper limit of the enlargement ratio (upper limit of the reduction ratio) may be other than 5%.

  Moreover, in the said embodiment, in Cell to Cell test | inspection, the example which compares the cell used as a test object with the cell arrange | positioned at the upper and lower sides and the right and left of the cell used as a test object is shown. However, the present invention is not limited to this. For example, in addition to the upper and lower sides and the left and right sides of the cell to be inspected, it may be compared with the diagonally upper right, diagonally upper left, diagonally lower right, and diagonally lower left cells (compared to a total of eight cells). Moreover, you may compare with the number of cells other than four and eight.

  In the above embodiment, an example in which the enlargement ratio or reduction ratio of the image is determined by the determination unit has been described, but the present invention is not limited to this. For example, if the cell size is known, the user can set the enlargement or reduction ratio so that the pattern pitch is approximately an integer multiple of the pixel resolution based on the known cell size and the known pixel resolution of the detection unit. And the user may input the calculated enlargement ratio or reduction ratio to the appearance inspection apparatus.

  In the above embodiment, an example is shown in which a plurality of cells are arranged in a matrix, but the present invention is not limited to this. For example, a plurality of cells may be arranged in a state other than a matrix.

40 Imaging unit 51 Inspection unit 52 Image adjustment unit 53 Determination unit 100 Appearance inspection device 220, 221, 222, 223, 224, 225, 226 cell

Claims (4)

An imaging unit that images a plurality of cells each having a repeating pattern;
An inspection unit for determining whether or not the cell is a non-defective product;
An image adjusting unit for enlarging or reducing the image of the plurality of cells captured so that the pitch of the pattern in the image of the plurality of cells captured is approximately an integer multiple of the pixel resolution of the inspection unit; With
The inspection unit collects the patterns straddling a plurality of adjacent cells in a plurality of enlarged or reduced images of the cells, and combines the combined patterns into a unit region of pixel resolution of the inspection unit. An appearance inspection apparatus configured to determine whether or not the cell is a non-defective product by comparing each cell.   The image adjustment unit enlarges the image of the plurality of cells captured at a magnification ratio equal to or lower than a predetermined magnification ratio, or the plurality of cells at a reduction ratio equal to or smaller than a predetermined reduction ratio. The visual inspection apparatus according to claim 1, wherein the visual inspection apparatus is configured to reduce an image of the image. Before the enlargement or reduction of the images of the plurality of cells by the image adjustment unit, further comprising a determination unit that determines the enlargement ratio or the reduction ratio of the images of the plurality of cells in advance,
The determination unit enlarges or reduces the image of the plurality of captured non-defective cells while changing the enlargement ratio or the reduction ratio, and also sets the pattern of the plurality of non-defective cells together. Comparing the images, the enlargement ratio or the reduction ratio is determined so that the difference between the brightness values of the images of the patterns grouped together in a plurality of non-defective cells becomes substantially zero. The visual inspection apparatus according to claim 2.   The inspection unit determines whether or not the cell is a non-defective product by comparing the patterns in which the predetermined number or less of the patterns are grouped together for each unit region of the pixel resolution of the inspection unit. The appearance inspection apparatus according to any one of claims 1 to 3, which is configured.

Images