JP2015148494A - Inspection device and inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce misinformation in an inspection and to accurately detect a defect.SOLUTION: In a line width measuring part 411, a line width of a plurality of positions of each linear pattern element in one substrate is measured based on a photographed image acquired for the substrate. In a standard line width correction part 412, a standard line width of a linear pattern element shown by standard line width information 48 generated from design data is corrected based on a representative value of the line width of the plurality of positions so as to generate corrected standard line width information. Subsequently, the line width of the plurality of positions of each linear pattern element in the substrate is measured based on the photographed image acquired for the other one substrate. In a defect detection part 413, a defect in the actual pattern of the substrate is detected by comparing each of the line width of the plurality of positions with the standard line width of the linear pattern element shown by the corrected standard line width information. As a result, misinformation in the inspection can be reduced and the defect in the actual pattern can be accurately detected.

Description

  The present invention relates to a technique for inspecting a pattern formed on a substrate.

  Conventionally, a pattern of a printed circuit board has been inspected. For example, in Patent Document 1, pattern dimensions in a specific direction are measured at a plurality of measurement positions for one inspection pattern in a grayscale image. In addition, reference data relating to the pattern dimension in a specific direction at the reference position corresponding to the measurement position in the gray image of the non-defective pattern serving as a comparison reference is prepared. And the presence or absence of the defect in a to-be-inspected pattern is determined by comparing the measurement data obtained from the measurement result, and the reference data.

  Also, the line width of each linear pattern element in the wiring pattern (actual pattern) on the printed circuit board is inspected with reference to the design line width of the linear pattern element in CAM (Computer Aided Manufacturing) data. For example, it is assumed that the design line widths of two linear pattern elements in an actual pattern are 60 μm and 120 μm, respectively, and that there are 20 μm chips in the two linear pattern elements. In this case, in the process of determining that a linear pattern element whose actual line width is 30% or more thinner or thicker than the design line width includes a defect, the linear pattern element having a design line width of 60 μm in the actual pattern includes a defect. It is determined that the linear pattern element having the design line width of 120 μm does not include a defect.

JP 2004-61118 A

  By the way, when a pattern is formed on a printed circuit board by etching as in the subtract method, the upper part of the linear pattern element may be thinner than the lower part as the etching proceeds. In such a linear pattern element, if the width of the lower part is substantially the design line width, there is no problem in its function. However, since the line width of the linear pattern element in the image obtained by imaging the printed circuit board is significantly different from the design line width of the linear pattern element, false information frequently occurs in the inspection using the design line width. On the other hand, in the above-described linear pattern element, for example, when there is a portion whose upper portion is not thinned only in part, such a portion is preferably detected as a defect from the viewpoint of appearance. However, it is difficult to detect only such a defect in the inspection using the design line width.

  The present invention has been made in view of the above-described problems, and has an object to reduce defects in inspection and to detect defects with high accuracy.

  The invention according to claim 1 is an inspection apparatus for inspecting a pattern formed on a substrate, and in a design pattern indicated by design data, a reference that is the line width of each linear pattern element having a certain line width A storage unit that stores a line width and reference line width information indicating a position of each linear pattern element, and an image showing the actual pattern by imaging a substrate on which the actual pattern is formed based on the design data An imaging unit that acquires an image, a line width measuring unit that measures line widths at a plurality of positions of the linear pattern elements in the actual pattern based on the captured image, and the imaging unit with respect to one substrate Based on the acquired captured image, the line width measurement unit measures line widths at a plurality of positions of the linear pattern elements, and the linear pattern elements indicated by the reference line width information indicate the line widths. By correcting the quasi-line width based on the representative values of the line widths at the plurality of positions, a reference line width correction unit that generates corrected reference line width information and the imaging unit with respect to another substrate Based on the acquired captured image, the line width measurement unit measures line widths at a plurality of positions of the linear pattern elements, and the correction reference line width information indicates each of the line widths at the plurality of positions. A defect detection unit configured to detect a defect in the actual pattern of the other substrate by comparing with a reference line width of each linear pattern element;

  The invention according to claim 2 is the inspection apparatus according to claim 1, wherein the reference line width information is a matrix obtained by dividing an area in which the design pattern is arranged into two dimensions, A pattern element map to which the same identification code is assigned to a plurality of matrix elements included in the region of each linear pattern element, the identification code of each linear pattern element, and the reference of each linear pattern element A line width table associated with the line width.

  Invention of Claim 3 is an inspection apparatus of Claim 2, Comprising: In the said pattern element map of the said reference line width information, with respect to the some linear pattern element in which the said design data shows the same line width And the reference line width correction unit is configured so that the representative value of the plurality of linear pattern elements is linear pattern elements that are separated from the reference line width by a predetermined value or more. A new identification code different from the identification code is given in the pattern element map, and a new reference line width based on the representative value is associated with the new identification code in the line width table.

  Invention of Claim 4 is an inspection apparatus in any one of Claim 1 thru | or 3, Comprising: Each of said one board | substrate and said other one board | substrate is a multilayer board | substrate, and the said imaging part is the said imaging | photography part. A captured image of the actual pattern formed on the outer substrate of the multilayer substrate is acquired.

  The invention according to claim 5 is an inspection method for inspecting a pattern formed on a substrate, and a) In the design pattern indicated by the design data, the line width of each linear pattern element having a constant line width is used. A step of preparing reference line width information indicating a certain reference line width and a position of each of the linear pattern elements; and b) obtained for one substrate on which an actual pattern is formed based on the design data. A step of measuring line widths at a plurality of positions of the respective linear pattern elements in the actual pattern based on a captured image indicating the actual pattern; and c) the reference line of each linear pattern element indicated by the reference line width information. Generating a corrected reference line width information by correcting the width based on a representative value of the line widths at the plurality of positions; and d) another one in which an actual pattern is formed based on the design data Measuring a line width at a plurality of positions of each of the linear pattern elements in the actual pattern based on a captured image acquired with respect to a board; and e) correcting each of the line widths at the plurality of positions. A step of detecting a defect in the actual pattern of the other substrate by comparing with a reference line width of each linear pattern element indicated by reference line width information.

  The invention according to claim 6 is the inspection method according to claim 5, wherein the reference line width information is a matrix obtained by dividing an area in which the design pattern is arranged into two dimensions, A pattern element map to which the same identification code is assigned to a plurality of matrix elements included in the region of each linear pattern element, the identification code of each linear pattern element, and the reference of each linear pattern element A line width table associated with the line width.

  The invention according to claim 7 is the inspection method according to claim 6, wherein, in the pattern element map of the reference line width information, the design data has a plurality of linear pattern elements having the same line width. The same identification code is assigned, and in the step c), among the plurality of linear pattern elements, the identification code is applied to a linear pattern element whose representative value is a predetermined value or more away from the reference line width. A new identification code different from is added in the pattern element map, and a new reference line width based on the representative value is associated with the new identification code in the line width table.

  The invention according to claim 8 is the inspection method according to any one of claims 5 to 7, wherein each of the one substrate and the other substrate is a multilayer substrate, and b) and d) ) In each of the steps, the captured image shows the actual pattern formed on the outer layer substrate of the multilayer substrate.

  ADVANTAGE OF THE INVENTION According to this invention, while reducing the false information in a test | inspection, the defect in an actual pattern can be detected accurately based on the corrected reference | standard line | wire width.

It is a figure which shows the structure of an inspection apparatus. It is a figure which shows the structure of a computer. It is a block diagram which shows the function structure in an inspection apparatus. It is a figure which shows the flow of the process which test | inspects a printed circuit board. It is a figure for demonstrating the production | generation of reference | standard line | wire width information. It is a figure which shows a pattern element map. It is a figure which shows a line | wire width table. It is a binary image which shows the real pattern on a printed circuit board. It is a figure which shows the cross section of a printed circuit board. It is a figure which shows a captured image. It is a figure which shows a captured image and a pattern element map. It is a figure which shows a correction pattern element map. It is a figure which shows a correction line | wire width table. It is a figure which shows a captured image.

  FIG. 1 is a diagram showing a configuration of an inspection apparatus 1 according to an embodiment of the present invention. The inspection apparatus 1 is an apparatus that inspects the appearance of a printed board 9 (also referred to as a printed wiring board) before electronic components are mounted, for example. The printed circuit board 9 to be inspected in the present embodiment is a multilayer board in which a plurality of boards on which electronic circuit patterns are formed are superimposed.

  The inspection apparatus 1 includes an apparatus main body 2 that captures an image of the printed circuit board 9 and a computer 5 that controls the overall operation of the inspection apparatus 1 and implements a calculation unit and the like described later. The apparatus main body 2 images the printed circuit board 9 to acquire a captured image (data) of multi-gradation, a stage 22 that holds the printed circuit board 9, and the stage 22 relative to the imaging device 21. The stage drive unit 23 moves in a moving manner. The imaging device 21 includes an illumination unit 211 that emits illumination light, an optical system 212 that guides the illumination light to the printed circuit board 9 and receives light from the printed circuit board 9, and an image of the printed circuit board 9 imaged by the optical system 212. An imaging unit 213 that converts an image into an electrical signal is included. The stage drive unit 23 includes a ball screw, a guide rail, a motor, and the like. The computer 5 controls the stage driving unit 23 and the imaging device 21 so that a predetermined area on the printed circuit board 9 is imaged.

  FIG. 2 is a diagram illustrating the configuration of the computer 5. The computer 5 has a general computer system configuration including a CPU 51 that performs various arithmetic processes, a ROM 52 that stores basic programs, and a RAM 53 that stores various information. The computer 5 is readable by a computer such as a fixed disk 54 for storing information, a display 55 for displaying various information such as images, a keyboard 56a and a mouse 56b for receiving input from an operator, an optical disk, a magnetic disk, a magneto-optical disk, etc. Further, a reading device 57 that reads information from the recording medium 8 and a communication unit 58 that transmits and receives signals to and from other components of the inspection device 1 are further included.

  In the computer 5, the program 80 is read from the recording medium 8 via the reading device 57 in advance and stored in the fixed disk 54. The CPU 51 executes arithmetic processing according to the program 80 while using the RAM 53 and the fixed disk 54.

  FIG. 3 is a block diagram showing a functional configuration in the inspection apparatus 1. In FIG. 3, the functional configuration realized by the CPU 51, the ROM 52, the RAM 53, the fixed disk 54, etc. of the computer 5 is represented by a broken-line rectangle denoted by reference numeral 5. Surrounding. The computer 5 includes a calculation unit 41 and a storage unit 49. The calculation unit 41 includes a line width information generation unit 410, a line width measurement unit 411, a reference line width correction unit 412, and a defect detection unit 413. The storage unit 49 stores reference line width information 48 generated based on design data such as CAM data (or CAD data). The reference line width information 48 includes a pattern element map 481 and a line width table 482. Details of functions realized by these configurations will be described later. In addition, these functions may be constructed by a dedicated electric circuit, or a dedicated electric circuit may be partially used.

  FIG. 4 is a diagram showing a flow of processing in which the inspection apparatus 1 inspects the printed circuit board 9. Here, it is assumed that a plurality of printed circuit boards 9 manufactured as one lot (hereinafter referred to as “target lot”) are inspection targets. The plurality of printed circuit boards 9 included in the target lot are the same product (semi-finished product) and are manufactured under the same conditions. In the inspection apparatus 1, first, reference line width information is obtained from design data used when forming a pattern on the outer layer substrate of the printed circuit board 9 (hereinafter, the actual pattern on the printed circuit board 9 is referred to as “actual pattern”). 48 is generated and prepared (step S11).

  FIG. 5 is a diagram for explaining the generation of the reference line width information 48. The design data indicates the design pattern 7 on the left side in FIG. 5, and the actual pattern on the plurality of printed circuit boards 9 included in the target lot is, for example, photolithography using a photomask indicating the design pattern 7. Formed using. That is, the actual pattern is formed on the printed circuit board 9 based on the design data. In the line width information generation unit 410 of the calculation unit 41, a linear pattern element 711 having a fixed line width (hereinafter, the line width indicated by the design data is referred to as “reference line width”) in the design pattern 7 indicated by the design data. Are extracted, and a plurality of pattern images showing only a set of linear pattern elements 711 each having the same reference line width are generated.

  For example, when the design pattern 7 includes a linear pattern element 711 having a reference line width of 50 μm, a linear pattern element 711 having a reference line width of 75 μm, and a linear pattern element 711 having a reference line width of 100 μm, FIG. As shown in the upper part on the right side, a pattern image 71 showing only a set of linear pattern elements 711 having a reference line width of 50 μm is acquired. Further, as shown in the middle part on the right side of FIG. 5, a pattern image 72 showing only a set of linear pattern elements 711 having a reference line width of 75 μm is acquired. As shown in the lower part on the right side of FIG. A pattern image 73 showing only a set of the linear pattern elements 711 is acquired. Each of the pattern images 71 to 73 is a matrix obtained by dividing the area where the design pattern 7 is arranged into two dimensions, and is a two-dimensional array of a plurality of matrix elements 70 (pixels). The resolution in the row direction and the column direction in the pattern images 71 to 73, that is, the size of the area on the printed circuit board 9 corresponding to one matrix element 70 is determined in advance.

  Subsequently, by assigning the same identification code to all the matrix elements 70 included in the set of linear pattern elements 711 in each pattern image 71 to 73, and synthesizing these pattern images 71 to 73, A pattern element map 481 shown in FIG. 6 is acquired. In the pattern element map 481 of FIG. 6, the identification code “1” is assigned to the matrix element 70 corresponding to the set of linear pattern elements 711 having a reference line width of 50 μm, that is, the matrix element 70 indicating the linear pattern elements 711 in the pattern image 71. Is attached. Further, an identification code “2” is assigned to the matrix element 70 corresponding to the set of linear pattern elements 711 having the reference line width of 75 μm, and the matrix element 70 corresponding to the set of linear pattern elements 711 having the reference line width of 100 μm is identified. Reference numeral “3” is attached. Further, an identification code “0” indicating the background is given to the matrix element 70 that is not included in any of the linear pattern elements 711. In FIG. 6, the matrix elements 70 included in each linear pattern element 711 are surrounded by thick lines, and the matrix elements 70 are indicated by parallel diagonal lines. The actual design pattern includes a region such as a drill hole. In the pattern element map 481, a predetermined identification code is assigned to the matrix element 70 included in the region such as the drill hole.

  The line width information generation unit 410 further generates a line width table 482 that associates each identification code of the linear pattern element 711 with the reference line width of the linear pattern element 711 as shown in FIG. In the line width table 482 of FIG. 7, the identification code “1”, the identification code “2”, and the identification code “3” are associated with a reference line width of 50 μm, a reference line width of 75 μm, and a reference line width of 100 μm, respectively.

  The line width table 482 also indicates the inspection items to be performed on the set of linear pattern elements 711 indicated by the respective identification codes, the lower limit rate of the line width, and the upper limit rate of the line width. The contents of the inspection item, the lower limit rate of the line width, and the upper limit rate of the line width will be described later. In the line width table 482, the parameter value (for example, the diameter of the drill hole) of the area may be associated with the identification code indicating the area of the drill hole or the like. The pattern element map 481 and the line width table 482 generated by the above processing are the reference line width information 48 indicating the reference line width of each linear pattern element 711 and the position of the linear pattern element 711 in the design pattern 7. Is stored in the storage unit 49.

  When the reference line width information 48 is prepared, the first printed circuit board 9 among the plurality of printed circuit boards 9 included in the target lot is placed on the stage 22 (see FIG. 1). 9 is arranged in an imaging area by the imaging unit 213. Then, a captured image showing an actual pattern is acquired by the imaging unit 213 and output to the calculation unit 41 (step S12). As described above, the printed circuit board 9 is a multilayer substrate, and the captured image of the actual pattern formed on the outer layer substrate of the multilayer substrate is acquired by the imaging unit 213. In the captured image, a plurality of pixels are arranged in the row direction and the column direction.

  Here, the captured image of the actual pattern acquired by the imaging unit 213 will be described. FIG. 8 is a binary image showing a part of an actual pattern on the printed circuit board 9, and an image obtained by binarizing a multi-tone captured image of the actual pattern acquired by the imaging unit 213 with a predetermined threshold value. Show. FIG. 9 is a view showing a cross section of the printed circuit board 9 at the position of the arrow AA in FIG. On the surface of the printed circuit board 9, a large number of linear pattern elements 91 are formed of a metal such as copper by a subtracting method, for example. In the following description, the same reference numerals 91 as the linear pattern elements on the printed circuit board 9 are given to the linear pattern elements in the image showing the actual pattern.

  In the formation of the pattern on the printed circuit board 9 which is a multilayer substrate, a relatively thick metal film (for example, a thickness of several tens of μm) is used to cover the side surface of the drill hole with the metal in the plating step before the etching step. Film) is formed. Although the reference line widths in the design data of the plurality of linear pattern elements 91 and 91a in FIG. 8 are the same, etching progresses in some areas on the printed circuit board 9 more than in other areas. As shown in FIG. 5, the upper part of some linear pattern elements 91a is thinner than the lower part. For example, the lower width W1 of the linear pattern element 91a is 100 μm, and the upper width W2 is 60 μm. Actually, in the region where the density of the linear pattern elements is low or in the region near the outer edge of the printed circuit board 9, the upper part of the linear pattern elements tends to be thinner than other regions. In the imaging unit 213, an image is acquired by focusing on the surfaces of the linear pattern elements 91 and 91a. Therefore, the width of the lower part is almost the reference line width, and the line width in the captured image of the linear pattern element 91a having no problem in its function is greatly different from the reference line width.

  In the following description, for easy understanding, a captured image 61 shown in FIG. 10 is referred to. The captured image 61 in FIG. 10 is acquired by imaging the printed circuit board 9 on which the actual pattern corresponding to the design pattern 7 on the left side in FIG. 5 is formed. The resolution in the row direction and the column direction in the captured image 61 is the same as the resolution in the row direction and the column direction in the pattern element map 481 in FIG. 6, and the number of pixels in the captured image 61 is the matrix element 70 in the pattern element map 481. Matches the number. The captured image 61 in FIG. 10 is simplified, and the actual captured image includes a large number of pixels.

  In the line width measurement unit 411, as shown in FIG. 11, one pixel 60a in the captured image 61 is specified as the target pixel. Subsequently, the identification code of the matrix element 70a at the same position as the target pixel 60a is specified in the pattern element map 481. The matrix element 70 to which the same identification code as that of the matrix element 70a is assigned is used as the target matrix element, and the line width direction of the linear pattern element 711 including the matrix element 70a is determined by a predetermined method from the array of the target matrix elements including the matrix element 70a. It is specified and determined as the line width direction in the target pixel 60a. In FIG. 11, the line width direction is indicated by an arrow with a symbol A1. When the line width direction is determined, the number of pattern pixels including the target pixel 60a and continuing in the line width direction is obtained using the pixel 60 indicating the linear pattern element 91 in the captured image 61 as the pattern pixel. In the present embodiment, the pattern pixel is a pixel having a value equal to or greater than a predetermined pattern threshold value. The number of pattern pixels continuous in the line width direction is the line width of the linear pattern element 91 at the position of the target pixel 60a, and the position (coordinates) of the target pixel 60a and the matrix element 70a corresponding to the target pixel 60a are identified. Stored with the code. When the target pixel 60a is not a pattern pixel, the line width of the linear pattern element 91 in the target pixel 60a cannot be used.

  The line width measurement unit 411 repeats the above process using all the pixels of the captured image 61 as the target pixel, so that the line width (unusable line) of the linear pattern elements 91 at the positions of all the pixels of the captured image 61 is obtained. Width is included). With the above processing, the line widths at a plurality of positions of each linear pattern element 91 in the actual pattern are measured based on the captured image 61 (step S13). Note that the line width measurement unit 411 may obtain the line width in an image obtained by binarizing the multi-tone captured image 61 with a pattern threshold value. In the pattern element map 481, when the same identification code is given to a set of linear pattern elements 711 having the same reference line width and the same longitudinal direction, each line width table 482 The line width direction of the linear pattern element 711 of the identification code may be included, and the line width direction may be specified by referring to the line width table 482.

  In the reference line width correction unit 412, one identification code among the plurality of identification codes used in the pattern element map 481 is specified as the attention identification code. Subsequently, in the pattern element map 481, among the plurality of matrix elements 70 to which the target identification code is assigned, a set of matrix elements 70 that are adjacent to each other and extend in the same direction is included in the same linear pattern element 711. Determined as element 70. Then, an average value of a plurality of line widths (excluding unusable line widths) obtained for the positions of the plurality of matrix elements 70 included in each linear pattern element 711 is used as a representative value of the line widths. Desired. Through the above processing, a plurality of matrix elements 70 of the pattern element map 481 included in each linear pattern element 711 of the target identification code are specified, and a representative value of the line width in the actual pattern is set for the linear pattern element 711. To be acquired. The representative value of the line width may be another statistical value such as a median value, and may be a value indicating the vicinity of the center in the distribution of a plurality of line widths obtained for each linear pattern element 711.

  Subsequently, the reference line width of the attention identification code is confirmed by referring to the line width table 482 using the attention identification code. In addition, among the linear pattern elements 711 of the attention identification code, each linear pattern element 711 whose representative line width is a predetermined value or more away from the reference line width of the attention identification code is specified as the specific linear pattern element 711. Then, a new identification code different from the target identification code is assigned to the plurality of matrix elements 70 included in the specific linear pattern element 711 in the pattern element map 481. In the line width table 482, the representative value of the line width of the specific linear pattern element 711 is associated with the new identification code as a reference line width. In addition, when the representative value of the line width of the specific linear pattern element 711 is more than a preset value with respect to the reference line width of the attention identification code, the fact is displayed on the display 55 and reported to the operator. It is preferred that The predetermined value used for specifying the specific linear pattern element 711 may be defined by a ratio (for example, 30%) with respect to the reference line width.

  In the reference line width correction unit 412, the above process is repeated using each of the identification codes in the pattern element map 481 as the target identification code. In this way, the pattern element map 481 and the line width table 482 are corrected (updated). That is, the reference line width of each linear pattern element 711 indicated by the reference line width information 48 is corrected based on the representative value of the line width in the actual pattern of the linear pattern element 711. As a result, new reference line width information (hereinafter referred to as “corrected reference line width information”) is generated (step S14). In the following description, the pattern element map and the line width table included in the correction reference line width information are referred to as a “correction pattern element map” and a “correction line width table”, respectively. Note that the new reference line width associated with the new identification code does not necessarily have to be the representative value itself, for example, a value based on the representative value, such as a value closest to the representative value among the values at regular intervals. That's fine.

  FIG. 12 is a diagram showing a correction pattern element map 481a included in the correction reference line width information, and FIG. 13 is a diagram showing a part of the correction line width table 482a included in the correction reference line width information. The correction pattern element map 481a in FIG. 12 and the correction line width table 482a in FIG. 13 are corrected based on the captured image 61 in FIG. In the actual pattern indicated by the captured image 61, the line widths of some of the linear pattern elements 91a and 91b are narrower than the reference line width (in FIG. 10, the linear pattern elements 91a and 91b having the reference line width are two. It is indicated by a dotted line). In the modified pattern element map 481a, a new identification code “4” is assigned to the matrix element 70 corresponding to the linear pattern element 91a of the actual pattern, and a new identification code “4” is assigned to the matrix element 70 corresponding to the linear pattern element 91b. 5 "is given. In the modified line width table 482a, a new reference line width of 30 μm is associated with the identification code “4”, and a new reference line width of 50 μm is associated with the identification code “5”.

  Further, the actual pattern shown by the captured image 61 in FIG. 10 includes a defect K such as a protrusion or a chip. In the corrected pattern element map 481a in FIG. 12, the matrix element 70 corresponding to the defect K is surrounded by a thick broken line. It is out. As described above, in the corrected reference line width information, since the representative value of the line width in the actual pattern of the linear pattern element 711 is obtained, the linear pattern element including the defect K depends only on the presence of the defect K. The identification code of 711 is not changed. In other words, the identification code of the matrix element 70 corresponding to the defect K is matched with the surrounding identification code.

  When the corrected reference line width information is generated, a captured image of the printed circuit board 9 to be inspected is acquired (step S15). Here, since the first printed circuit board 9 is also an inspection target, the process in step S15 is omitted, and the captured image acquired in the process in step S12 is used. Subsequently, in the line width measurement unit 411, as in step S13, one pixel 60a is specified as the target pixel in the captured image 61 (see FIG. 11), and the line of the linear pattern element 91 at the position of the target pixel 60a is identified. A width is required. The line width at the position of the target pixel 60 a is output to the defect detection unit 413.

  In the defect detection unit 413, the identification code of the matrix element 70a at the same position as the target pixel 60a is specified as the target identification code in the correction pattern element map 481a, and the correction line width table 482a is referred to using the target identification code, Inspection items are confirmed (see FIG. 7). When the inspection item is “line width narrowing”, the lower limit value of the line width is obtained by subtracting the value obtained by multiplying the reference line width of the object identification code by the lower limit rate from the reference line width. When the line width of the linear pattern element 91 at the position of the target pixel 60a is smaller than the lower limit value, the line width of the linear pattern element 91 of the actual pattern becomes excessively thin at the position of the target pixel 60a. The position of the pixel of interest 60a is included in the list of “line width narrowing” defects. When the inspection item is “thickening line width”, the upper limit value of the line width is obtained by adding the value obtained by multiplying the reference line width of the target identification code by the upper limit rate to the reference line width. . When the line width of the linear pattern element 91 at the position of the target pixel 60a is larger than the upper limit value, the line width of the linear pattern element 91 of the actual pattern is excessively thick at the position of the target pixel 60a. Therefore, the position of the pixel of interest 60a is included in the defect list of “thickening line width”. Note that the above processing is omitted when the line width at the target pixel 60a is not available or when no inspection item is assigned to the target identification code in the modified line width table 482a.

  Actually, the above processing is repeated by the line width measurement unit 411 and the defect detection unit 413 with all the pixels of the captured image 61 as the target pixel. As described above, the line widths at a plurality of positions of each linear pattern element in the actual pattern are measured based on the captured image 61 (step S16), and each of the line widths at the plurality of positions is corrected reference line width information. Is detected in the actual pattern of the printed circuit board 9 (step S17).

  When the inspection for the first printed circuit board 9 is completed, the second printed circuit board 9 included in the target lot is imaged, and the captured image 62 shown in FIG. 14 is acquired (steps S18 and S15). Then, the line width is measured at each position based on the captured image 62, and the defect is detected by comparing the line width with the reference line width (steps S16 and S17). As described above, since the plurality of printed circuit boards 9 included in the target lot are manufactured under the same conditions, even in the second printed circuit board 9, as shown in FIG. , 91b is narrower than the reference line width (reference line width before correction) in the design data. In the inspection apparatus 1, the defect K is detected for these linear pattern elements 91a and 91b based on the reference line width indicated by the corrected line width table 482a. If the process of said step S15-S17 is performed with respect to all the printed circuit boards 9 contained in an object lot, the process in the test | inspection apparatus 1 will be completed (step S18). The corrected reference line width information generated for the target lot may be used for the inspection of the printed circuit board 9 of another lot.

  Here, a process of a comparative example used for detecting a defect of an actual pattern without correcting the reference line width information 48 will be described. In the process of the comparative example, the reference line width in the design data is also used for some linear pattern elements 91a and 91b whose upper part is thinner than the lower part. Therefore, the width of the lower part is almost the reference line width, and most of the linear pattern elements 91a and 91b having no problem in function are detected as defects, and false information is frequently generated. On the other hand, in the linear pattern elements 91a and 91b, for example, when there is a portion whose upper portion is not thin only in a part, such a portion is preferably detected as a defect from the viewpoint of appearance. However, since the reference line width in the design data is used in the process of the comparative example, it is difficult to detect such a defect.

  On the other hand, in the inspection apparatus 1, the line widths at a plurality of positions of each linear pattern element in the actual pattern of the printed circuit board 9 are measured based on the captured image acquired for one printed circuit board 9. Then, the corrected reference line width information is generated by correcting the reference line width of the linear pattern element indicated by the reference line width information 48 based on the representative values of the line widths at the plurality of positions. Further, the line widths at a plurality of positions of the respective linear pattern elements in the actual pattern of the printed board 9 are measured based on the captured image acquired for the other printed board 9. Then, by comparing each of the line widths at the plurality of positions with the reference line width of the linear pattern element indicated by the corrected reference line width information, a defect in the actual pattern of the printed circuit board 9 is detected. As a result, even when a linear pattern element with a thin upper part is formed in the actual pattern, it is possible to reduce the false alarm in the inspection based on the captured image showing the surface of the actual pattern, and the corrected It is possible to accurately detect a defect in an actual pattern based on the reference line width. The inspection apparatus 1 may be used for inspecting a linear pattern element having a thick upper portion.

  The reference line width information 48 includes a pattern element map 481 and a line width table 482, and a corrected pattern element map 481a and a corrected line width table 482a are generated when the printed circuit board 9 is inspected. Then, the line width of the linear pattern element is measured at the position in the captured image corresponding to each matrix element 70 of the correction pattern element map 481a, and the line width table 482 is stored using the identification code of the matrix element 70. The reference line width of the linear pattern element is specified by referring to it. Thereby, it becomes possible to detect a defect with high definition and efficiency.

  The inspection apparatus 1 can be variously modified.

  The line width measurement unit 411 does not need to measure the line width at all positions (pixels) of each linear pattern element in the captured image, and is arbitrarily determined depending on the measurement accuracy required by the inspection apparatus 1. The line width may be measured only at a plurality of measurement points. Also in this case, the line widths of the plurality of measurement points of each linear pattern element are measured, and the reference line width of the linear pattern element indicated by the reference line width information 48 is set to the representative value of the line widths of the plurality of measurement points. By correcting based on this, it is possible to reduce false information in inspection and to detect defects with high accuracy.

  The reference line width information 48 does not necessarily include the pattern element map 481 and the line width table 482. For example, the line width is measured only at a plurality of arbitrarily determined measurement points as described above. In this case, reference line width information indicating only the coordinates of each measurement point and the reference line width at the measurement point may be prepared. Such reference line width information can also be said to substantially indicate the reference line width of each linear pattern element and the position of the linear pattern element.

  In the above embodiment, the content of the line width table 482 is simplified by assigning the same identification code to a plurality of linear pattern elements whose design data has the same line width in the pattern element map 481. However, when the number of linear pattern elements included in the design pattern is relatively small, an identification code may be assigned to each linear pattern element. In the reference line width information 48 to which an identification code is assigned for each linear pattern element, the reference line width may be corrected to a representative value of the line width in all the linear pattern elements.

  The substrate to be inspected in the inspection apparatus 1 may be an inner layer substrate of a printed board, a semiconductor substrate, a glass substrate, or the like. The inspection apparatus 1 can inspect patterns formed on various substrates.

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Inspection apparatus 7 Design pattern 9 Printed circuit board 48 Reference line width information 49 Memory | storage part 61,62 Captured image 70,70a Matrix element 91,91a, 91b (actual pattern) Linear pattern element 213 Imaging part 411 Line width measurement part 412 Reference line width correction unit 413 Defect detection unit 481 Pattern element map 481a Correction pattern element map 482 Line width table 482a Correction line width table 711 Linear pattern element (of design pattern) K Defects S11 to S18 Steps

Claims (8)

An inspection apparatus for inspecting a pattern formed on a substrate,
In the design pattern indicated by the design data, a storage unit that stores a reference line width that is the line width of each linear pattern element having a certain line width, and reference line width information that indicates a position of each linear pattern element;
An imaging unit that obtains a captured image indicating the actual pattern by imaging a substrate on which the actual pattern is formed based on the design data;
A line width measuring unit that measures line widths at a plurality of positions of the linear pattern elements in the actual pattern based on the captured image;
Based on the captured image acquired by the imaging unit with respect to one substrate, the line width measurement unit measures line widths at a plurality of positions of the linear pattern elements, and the lines indicated by the reference line width information A reference line width correction unit that generates correction reference line width information by correcting the reference line width of the pattern element based on a representative value of the line widths of the plurality of positions;
Based on a captured image acquired by the imaging unit with respect to another substrate, the line width measuring unit measures line widths at a plurality of positions of the linear pattern elements, and the line widths at the plurality of positions are measured. A defect detection unit that detects a defect in the actual pattern of the other one substrate by comparing each of them with a reference line width of each linear pattern element indicated by the correction reference line width information;
An inspection apparatus comprising: The inspection apparatus according to claim 1,
The reference line width information is
A pattern element obtained by dividing an area in which the design pattern is arranged into two dimensions, and the same identification code is given to a plurality of matrix elements included in the area of each linear pattern element Map and
A line width table associating the identification code of each linear pattern element with the reference line width of each linear pattern element;
The inspection apparatus characterized by including. The inspection apparatus according to claim 2,
In the pattern element map of the reference line width information, the same identification code is given to a plurality of linear pattern elements in which the design data shows the same line width,
The reference line width correcting unit assigns a new identification code different from the identification code to a linear pattern element whose representative value is a predetermined value or more away from the reference line width among the plurality of linear pattern elements. An inspection apparatus which is given in a pattern element map and associates a new reference line width based on the representative value with the new identification code in the line width table. The inspection apparatus according to any one of claims 1 to 3,
Each of the one substrate and the other one substrate is a multilayer substrate;
The inspection apparatus, wherein the imaging unit acquires a captured image of the real pattern formed on an outer substrate of the multilayer substrate. An inspection method for inspecting a pattern formed on a substrate,
a) preparing a reference line width that is the line width of each linear pattern element having a certain line width in the design pattern indicated by the design data, and reference line width information indicating a position of each linear pattern element; ,
b) Line widths at a plurality of positions of the respective linear pattern elements in the actual pattern based on a captured image showing the actual pattern acquired with respect to one substrate on which an actual pattern is formed based on the design data Measuring the
c) generating the corrected reference line width information by correcting the reference line width of each linear pattern element indicated by the reference line width information based on a representative value of the line widths at the plurality of positions;
d) Measuring line widths at a plurality of positions of the respective linear pattern elements in the actual pattern based on a captured image acquired for another substrate on which an actual pattern is formed based on the design data. Process,
e) Detecting a defect in the actual pattern of the other substrate by comparing each of the line widths at the plurality of positions with a reference line width of each of the linear pattern elements indicated by the corrected reference line width information. And a process of
An inspection method comprising: The inspection method according to claim 5,
The reference line width information is
A pattern element obtained by dividing an area in which the design pattern is arranged into two dimensions, and the same identification code is given to a plurality of matrix elements included in the area of each linear pattern element Map and
A line width table associating the identification code of each linear pattern element with the reference line width of each linear pattern element;
The inspection method characterized by including. The inspection method according to claim 6,
In the pattern element map of the reference line width information, the same identification code is given to a plurality of linear pattern elements in which the design data shows the same line width,
In the step c), among the plurality of linear pattern elements, a new identification code different from the identification code for the linear pattern element whose representative value is separated from the reference line width by a predetermined value or more is the pattern element. An inspection method, characterized in that a new reference line width based on the representative value is associated with the new identification code in the line width table. The inspection method according to any one of claims 5 to 7,
Each of the one substrate and the other one substrate is a multilayer substrate;
In each of the steps b) and d), the captured image shows the actual pattern formed on the outer layer substrate of the multilayer substrate.

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