JPH036410A - Inspecting apparatus for pattern - Google Patents

Abstract

PURPOSE:To prevent a false information and thereby to enable execution of accurate inspection by detecting characteristics on the shape and width of a wiring pattern with regard to both a reference board and a board for inspection and by judging from combination of the characteristics whether the characteristics have a defective pattern or not. CONSTITUTION:An (xy) table 12 whereon a sample board 11 is mounted moves in the direction (y) in synchronization with a line sync clock supplied from a terminal 21, and when scanning in the direction of the board 11 is ended, the table moves in the direction (x). After this movement, subsequently, scanning is made in the direction (y) again reversely to the previous one, so that the whole surface of the board 11 be scanned. A distance of movement at this time is determined on the basis of the image formation magnification of a lens 14 and the number of elements of a CCD line sensor 15. Next, the board 11 is illuminated by a lamp 13 and a reflected light is magnified and imaged on the sensor 15 by the lens 14. Then, an analog image signal 17 is inputted to an analog comparator 18 and binary-coded at a threshold value level supplied from a terminal 19.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pattern inspection apparatus for inspecting wiring patterns on printed circuit boards and masks for defects.

BACKGROUND OF THE INVENTION As the density of mounting electronic components on printed circuit boards increases, wiring patterns on circuit boards are becoming more detailed and complex. Visual appearance inspection has been used to inspect wiring patterns for defects, but visual inspection has become difficult as wiring patterns become more dense. Against this background, there is a demand for the development of a pattern inspection device that can accurately and quickly inspect wiring patterns.

Conventional pattern inspection apparatuses perform defect detection processing on binary data obtained by scanning and decomposing an original image using inspection methods broadly classified as a comparison method and a design rule method. The comparison method performs pattern matching between a non-defective pattern or CAD wiring pattern design data and the wiring pattern of the test board, and although precise positioning is required, accurate testing is possible. (For example, JP-A-60-2
63807) On the other hand, the design rule method is based on pattern design rules such as wiring width and pattern arrangement relationships.
This method measures the width of the inspection pattern and the feature values that indicate the relationship between patterns and inspects whether the design rules are violated, and the feature is that it can be inspected from the first sheet without preparing a standard pattern. have (For example, JP-A-62
-299711 Publication) Problems to be Solved by the Invention However, the above-mentioned comparison method requires a large-capacity storage device for storing the standard pattern or two input devices for simultaneously inputting the standard pattern and the test pattern. This results in a large-scale equipment configuration. In addition, the design rule method is used to compare the characteristic quantities of defective patterns with certain design standards, so if there are special patterns or character symbols for surface mount components such as outer layer boards, these patterns are considered as defects. In order to detect this, it is necessary to mask the relevant area at the beginning of the inspection.

The present invention solves the above-mentioned problems and provides a pattern inspection device that can perform accurate inspection without false alarms.

Means for Solving the Problems In order to achieve the above objects, the present invention provides pattern detection means for optically detecting the wiring pattern of a target board and performing photoelectric conversion, and converting the photoelectrically converted input signal into binary image data. Binarization means for converting, and pattern shape determination means for scanning the binary data with a scanning window and determining whether the shape of the pattern within the window matches a predetermined logic when the center position of the window detects an edge of the pattern. a pattern width determining means for measuring a continuous length of the pattern on a straight line passing through the center of the window at the window scanning position where the edge of the pattern is detected and determining whether the pattern matches a predetermined condition; A feature determining means that determines whether or not the scanning position has the characteristics of a defective pattern based on a combination of pattern width determination results, and outputs a determination code and position information as feature data if it is a defect;
a feature data switching means for switching a storage location of the feature data depending on whether the input cover pattern is a standard pattern or an inspection pattern; a means for storing the feature data of the standard pattern; a means for storing feature data of the inspection pattern; Comparison/determination means is provided which compares the feature data of the standard pattern and the inspection pattern, and determines that the pattern is defective if the same feature does not exist at the same position.

Effect of the Invention With the above configuration, the present invention detects and stores defect characteristic data and its position information in both the standard pattern and the inspection pattern. By canceling out the feature data when there is the same feature data and determining it as a defect when there is mutually different feature data, even if there are special patterns or character symbols on the inspection target, there is no need for masking work. This makes it possible to carry out thorough inspections.

Embodiment FIG. 1 is a block diagram of a pattern inspection apparatus in an embodiment of the present invention. In Fig. 1, l is a pattern detection means that optically detects the wiring pattern of the target board and performs photoelectric conversion, and 2 is a pattern detection means that samples the photoelectrically converted input signal at a predetermined pitch and is fixed at a Hell's threshold value of 2. The binarization means 3 scans the binary data with a scanning window, and when the center position of the window detects the edge of the pattern, it compares the shape of the pattern inside the window with a predetermined logic and calculates the edge of the pattern. A pattern shape determining means 4 measures the continuous length of the pattern on a straight line passing through the center of the window at the window scanning position where the edge of the pattern is detected, and determines whether the pattern matches a predetermined condition. The pattern width determining means 5 determines whether the scanning position has the characteristics of a defective pattern based on the combination of the pattern shape and the result of the cross-turn width determination, and if it is a defect, outputs the determination code and position information as characteristic data. Feature determining means; 6, feature data switching means for switching the storage location of the judgment code and position information depending on whether the input cover pattern is a standard pattern or a test pattern; 7, standard data storage means for storing feature data of the standard pattern;
Reference numeral 8 denotes a test data storage means for storing characteristic data of the test pattern, and reference numeral 9 denotes a comparison determination means for comparing the characteristic data stored in the standard data and test data storage means 7.8 and determining differences.

In the above configuration, its operation will be explained below along with its detailed configuration. Figure 2 shows pattern detection means 1 and 2.
FIG. 2 is a specific configuration diagram of the value converting means 2. FIG.

In FIG. 2, 11 is a sample substrate, 12 is an xy table 13 is an illumination lamp, 14 is a lens for imaging the inspection pattern, and 15 is a CCD that photoelectrically converts the reflected light from the sample substrate 11.
A line sensor, 16, a clock pulse generation circuit that supplies clock pulses to the CCD line sensor 15, 17, C
An analog image signal photoelectrically converted by the CD line sensor 15, 18 an analog comparator, 19 a terminal for supplying a comparison reference potential to the analog comparator 18, 20 an output terminal for binary image data, 21 and 22 will be described later. Terminals 23 and 24 that supply a line synchronization clock and pixel transfer lock to the image signal processing system are fixing pins that fix the sample substrate 11 to the xy child table 2. With the above configuration, the sample substrate 11
The χy child table 2 mounted thereon moves in the X direction in synchronization with the line synchronization clock supplied from the terminal 21, and moves L in the X direction when scanning in the direction of the substrate is completed. After the movement, it scans again in the X direction in the opposite direction to the previous scan to scan the entire surface of the substrate. L is determined by the following equation based on the imaging magnification of the lens 14 and the number m of elements of the CCD line sensor 15.

L=k・δ・ (m-me) ■(δ here
is the element size of the CCD line sensor, and mo is the number of pixels in overlap scanning. ) The sample substrate 11 is the lamp 13
The reflected light is magnified and imaged onto the CCD line sensor 15 by the lens 14.

The analog image signal 17 is input to an analog comparator 18 and binarized at a predetermined threshold level supplied from a terminal 19.

Next, pattern shape determining means 3, pattern width determining means 4,
Image signal processing in the feature determining means 5, feature data switching means 6, standard data storage means 7, and inspection data storage means 8 will be explained with reference to FIG. First, terminal 31
The binary image data inputted from is scanned by an nXn scanning window, and the pattern shape and pattern width within the window are determined by pattern shape determining means 3 and pattern width determining means 4.

Note that the window scanning circuit using a line memory and shift register in the binarization means 2 is a well-known technique, and its explanation will be omitted. FIG. 4 shows a specific determination method of the pattern shape determination means 3. FIG. 4(a) shows a pattern shape determination mask. First, edges of the wiring pattern are detected using the 3×3 mask 52 using the following equation.

do ・ (dl+d3+d5+d7) ・ (+L
+d3+ds+d7) -■When the value of formula ■ is 1,
The center position of the window (do position) is on the edge of the wiring pattern. At this time, the shape of the edge is classified into a straight line, concave, convex, or irregular pattern depending on the arrangement of the patterns in the ring area 51. The figure shows a case where the radius of the ring is 3. When there is only one continuous black pixel region in the ring region, the shape is classified as shown in the pattern shape determination table of FIG. 4(f) based on the difference in the number of pixels between the black region and the white region. When there are a plurality of black areas in the switching area 51 ((e) in the same figure), it is determined that the pattern is irregular. (b), (C), and (d) of FIG. 4 show cases of straight, concave, and convex shapes, respectively.

The judgment result of the pattern shape judgment table is written in a ROM as a 2-bit code, and the result is written to the ROM as a 2-bit code, and the result is written to the ROM as a 2-bit code. -als is used as an address to refer to the ROM and output the determination result.

FIG. 5 shows a specific determination method of the pattern width determination means 4. In this embodiment, a pattern width of 6 to 7 pixels and a clearance of 8 pixels or more are considered normal.

FIG. 5(a) shows a pattern width determination mask. When the window center position (shaded position in the figure) is on the edge of the wiring pattern, pattern detection pixels are arranged in eight directions from the center pixel. Then, consecutive black pixels in each direction are counted and the minimum value is selected as the pattern width.

FIG. 5(b) shows a specific configuration diagram thereof. Ao and B.

The comparator 61 outputs A as the MSB. -A, and B0~B.

The selector 67 selects the smaller value. Similarly, the comparator 62 and selector 68 select 00 to C1. -D, and select the smaller value. The smaller value of the two values selected by the selectors 67 and 68 is further selected by the comparator 65 and the selector 71, and the priority encoder 73 converts it into a length measurement value. 45
Similarly, comparators 63.64.66 and selectors 69.70.7 for the 135°, 225°, and 315° directions
2 and E using priority encoder 74. "E
Find the minimum length measurement value among b, Fo''Fb, Go-Gb, and H8-H6.The OR circuit 76 and the gate circuit 77 are provided to check minimum clearance violation.For example, A. 0 and A8 is 1, it is detected as a minimum clearance violation.The pattern width determination table 75 is created using a total of 8 bits: 4 bits output from the priority encoder 73, 3 bits output from the priority encoder 74, and 1 bit output from the OR circuit 76. See.

The determination contents are written in the ROM in 2-bit code as shown in the following table.

Margins below Now, in FIG. 3, the feature determining means 5 uses the pattern shape and pattern width determined by the pattern shape determining means 3 and the pattern width determining means 4 to determine whether the pattern is a defective characteristic pattern or not. However, if it has the characteristics of a defect, its determination code is stored in the standard data storage means 7 or the inspection data storage means 8 together with the coordinate count value. The characteristic data switching means 6 is provided to switch the storage destination of the determination result to the standard data storage means 7 or the inspection data storage means 8 depending on whether the input cover pattern is a standard board or a test board, and its control is based on the line period clock. terminal 34
The pixel transfer is performed from the Y counter 35 to the pixel transfer lock terminal 36 to the X counter 3. Then, by applying a switching signal to the terminal 33 from the outside, the storage destination is switched.

FIG. 6 shows specific determination contents by the feature determination means 5. It is determined whether or not the pattern has a defective feature using a total of 4 pinpoints, including the upper 2 bits of the shape determination code and the lower 2 bits of the line width determination code. As shown in FIG. 6, when the determination code is 0001.0010.01 old or 1001.1010, and when the upper 2 bits or lower 2 bits are 11, it is determined that there is a defective feature.

FIGS. 7(a) and 7(b) show the storage contents of the memory of the standard data storage means 7 and the memory of the test data storage means 8, which store standard data and test data. A total of 3 words, 1 word for the scanning line number and judgment code, 1 word for the X coordinate, and 1 word for the X coordinate, are stored as a set of feature data in the scanning order. The scanning line number is as shown in FIG. 7(C).
It shows the number of the scanning line of the CCD line sensor 15 on the sample substrate 11.

In the comparison/judgment means 9 in FIG. 1, the memory of the standard data storage means 7 and the memory of the inspection data storage means 8 are accessed by a microcomputer to compare and determine the characteristic data. FIG. 8 shows the processing procedure for comparison and determination. First, in 81, first standard data (judgment coat CH1X coordinate Xo, V coordinate YH) and inspection data (judgment coat Cyu, YX)
I Read. Next, in 82, the magnitude of the position coordinates of the standard data and the inspection data is compared, and if the position of the standard data exceeds the position of the inspection data, the undetermined standard data remains in the memory of the standard data storage means 7 in 83. If there is, the next standard data is read in 84 and the determination in 82 is made again.

If the position of the inspection data reaches or does not reach the position of the standard data in the determination at 82, the coincidence determination between the standard data and the inspection data is performed at 85, and if they do not match, the undetermined inspection data is stored in the inspection data storage means 8 at 86. If it remains, the next test data is read in 87 and subjected to the determination in 82 again. 8
If the standard data and inspection data match in the determination in step 5, the standard data and inspection data are erased from the memory. Then, in 89, it is determined whether the undetermined standard data and inspection data remain in the memory of the standard data storage means 7 and the memory of the inspection data storage means 8, and if they remain, the next standard data and inspection data are stored in 90. is read and subjected to judgment 82 again. By comparing the magnitudes of the position coordinates Lj in 82 and 85 with respect to the predetermined upper bits of the binary data without indicating the coordinates, the determination can be made without being affected by minute positional deviations between the standard board and the test board. I can do it.

The above process is repeated until there is no more undetermined feature data, and finally the feature data remaining in the memory of the standard data storage means 7 and the memory of the inspection data storage means 8 indicates the position and characteristics of the defect.

Effects of the Invention As described above, the present invention detects features related to the shape and width of wiring patterns on both standard boards and test boards,
It is determined whether the defect pattern 5 has the characteristics based on the combination of the characteristics, and if it is determined that the defect pattern has characteristics, the position coordinates and the determination result are stored, and the stored standard data and inspection data are compared. This prevents false alarms due to the presence of special patterns or character symbols on the test board, allowing accurate testing.

[Brief explanation of drawings]

FIG. 1 is a block wiring diagram of a pattern inspection device according to an embodiment of the present invention, FIG. 2 is a block wiring diagram of main parts of the pattern detection means and binarization means in the same device, and FIG. 3 is a block wiring diagram of main parts of the same device. a block diagram of pattern shape determination means, pattern width determination means, feature determination means, characteristic data switching means, standard data storage means, and inspection data storage means;
FIG. 4 is a conceptual diagram showing the determination method in the pattern shape determination means, FIGS. 5(a) and (b) are conceptual diagrams and detailed block wiring diagrams showing the determination method in the pattern width determination means, and FIG. Fig. 7 is a conceptual diagram showing the storage contents of feature data in the standard data storage means and inspection data storage means, and Fig. 8 is a processing procedure in the comparison judgment means. FIG. ■... Pattern detection means, 2... Binarization means, 3... Pattern shape determination means, 4...
... pattern width determination means, 5--characteristic determination means,
6...Characteristic data switching means, 7...Standard data storage means, 8...Test data storage means, 9.
...Comparative judgment means.

Claims (3)

[Claims] (1) A pattern detection means that optically detects and photoelectrically converts a wiring pattern formed on a printed circuit board or a photomask, and a binarization means that samples the photoelectrically converted signal at a predetermined pitch and converts it into binary data. , 2 above
a pattern shape determination means for scanning value data through a window and determining the shape of the pattern by comparing the pattern structure within the window with a predetermined logic when the center position of the window is on the pattern; A pattern width determination means that measures the width of a passing pattern and determines whether the measured value matches a predetermined condition, and determines whether or not the pattern is a defective pattern from a combination of the pattern shape and the pattern width determination result. a feature determining means for outputting the determination code and the scanning position of the window as feature data; a feature data switching means for switching the storage destination of each feature data of the input of the standard pattern and the input of the inspection pattern; and the feature data switching means standard data storage means for storing characteristic data of the standard pattern by switching the characteristic data; inspection data storage means storing characteristic data of the inspection pattern by switching the characteristic data switching means; and the standard data storage means and the inspection. A pattern inspection device comprising a comparison and determination means for comparing feature data stored in a data storage means and determining a difference. (2) When the edge of the pattern is detected and the center position of the scanning window is on the edge, the pattern shape determining means determines the unevenness of the edge from the area ratio occupied by the pattern within a ring area of a predetermined size radius with respect to the center position. The pattern inspection device according to claim 1, wherein the pattern inspection device makes a determination. (3) When the edge of the pattern is detected and the center position of the scanning window is on the edge, the pattern width determination means determines the minimum pattern width among the widths of patterns that are continuous on a straight line passing through the center position in a predetermined direction. 2. The pattern inspection apparatus according to claim 1, wherein the pattern inspection apparatus selects and compares and determines the line width with a standard line width.