JPH04213778A - Pattern matching device - Google Patents

Abstract

PURPOSE:To offer the pattern matching device for executing correctly pattern matching with regard to the pattern matching device for deriving a position of a master pattern. CONSTITUTION:A matching deciding part 11 compares a master pattern and an image pickup pattern, and derives a position in which the number of unmatching between each dot of both the patterns is the smallest. A matching degree calculating means 12 calculates separately the degree of matching of a black dot and the degree of matching of a white dot of both the patterns, respectively, in a position in which the number of unmatching between each dot of both patterns is smallest. A matching degree calculating means 13 calculates the degree of pattern matching, based on both the degrees of matching of the black dot and the white dot.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern matching apparatus, and more particularly to a pattern matching apparatus for determining the position of a master pattern. In each manufacturing process of semiconductor integrated circuits (ICs), in order to accurately expose and wire a sample, it is necessary to determine the position of the master pattern set on the sample and accurately position the sample relative to the equipment. .

0002

2. Description of the Related Art FIG. 3 shows a block diagram of an example of a conventional pattern matching device. In the figure, the central processing unit (CP
U) stores in advance a master pattern, which is a reference pattern when performing pattern matching, in a built-in memory. Also, a television (TV) camera 2 as an imaging device
2 images a comparison pattern on the sample.

For example, when positioning an IC chip, a TV camera 22 takes an image of the sample, that is, the IC chip. At this time, as shown in FIG. 4, master patterns 32 and 33 are formed in advance on the IC chip 31, for example, at the upper left corner and lower right corner where the wiring pattern is located. The master patterns 32 and 33 are, for example, as shown in FIG. 5A, a so-called 8×4 dot pattern consisting of 8 dots (pixels) in the horizontal direction and 4 dots in the vertical direction, a total of 32 dots, among which are indicated by diagonal lines. Assume that 4 dots are black and the remaining 28 dots are white.

The CPU 21 in FIG. 3 stores the original combination pattern of black dots and white dots of this master pattern as a reference pattern in its built-in memory, and reads out this stored reference pattern (master pattern) and sends it to the memory 23. Store it. On the other hand, the TV camera 22 takes an image of the IC chip 31 and digitally processes the image information within the imaging range, and then stores it in the memory 24 . Here, TV
The matching screen cut out from the imaging range of the camera 22 has a size as shown by a broken line 34 in FIG.

The matching determination unit 25 in FIG. 3 compares the master pattern from the memory 23 and the imaged pattern from the memory 24 (that is, the comparison pattern on the matching screen 34), and determines the number of mismatches between each dot of both patterns. Find the position where is the least. Here, matching determination unit 2
5, as shown in FIG. 6, among the image information in the matching screen 34, the image information pattern in the comparison area 35 having the same size of 8×4 dots as the master patterns 32 and 33 and the master pattern are arranged between each dot. The dots are compared to see if they have the same value, and the number of mismatched dots is counted and stored. When the process is completed, the comparison area 35 is shifted to the right by one dot and the above-mentioned comparison and counting between each dot is performed again. Thereafter, in the same manner as described above, the comparison area 35 is sequentially shifted from the upper left to the lower right of the matching screen 34, and comparison with each dot of the master pattern and counting of the number of mismatched dots (pattern matching) are performed.

In this way, the matching determining section 25 performs pattern matching and determines that the position with the least number of mismatched dots is the position where a pattern closest to the master pattern 32 can be obtained, and stores the position coordinates in the register 26. do. The position coordinates stored in the register 26 are notified to the outside of the matching circuit 30.

[0007]

However, the comparison pattern of the matching screen 34 obtained by imaging with the TV camera 22 is different from the combination pattern of black dots and white dots obtained by accurately imaging the master pattern 32 or 33. In some cases, the entire matching screen 34 appears white depending on the condition of the light hitting the IC chip 31, the surface of the IC chip 31, etc., and therefore the comparison pattern of the comparison area 35 is also shown in FIG. 5(B). It is possible that all 32 dots become white dots.

In this case, since the entire matching screen 34 is white, it should not be possible to position the IC chip 31, but the master pattern shown in FIG.
), the number of mismatched dots is only 4, so the degree of matching is 87.
．． It becomes 5% (=(32-4)×100/32). Therefore, in this case, matching will be achieved at any position on the matching screen 34.

[0009] Furthermore, the master patterns 32 and 33 are white,
When the number of dots is half black, if pattern matching is performed with a comparison pattern of all dots white or black, the degree of matching will be 50%, but in reality, the master pattern 32
, 33, when the ratio of white dots to black dots is about 20:80, it is easier to take a characteristic pattern in both the vertical and horizontal directions as a master pattern, so the pattern matching will still be achieved.

[0010] The present invention has been made in view of the above points.
An object of the present invention is to provide a pattern matching device that performs accurate pattern matching.

[0011]

[Means for Solving the Problems] FIG. 1 shows a diagram of the basic configuration of the present invention. In the figure, a matching determination unit 11 compares the master pattern and the imaged pattern to find a position where the number of mismatches between each dot of both patterns is the least. The degree of coincidence calculating means 12 separately calculates the degree of coincidence of black dots and the degree of coincidence of white dots in the master pattern and the imaged pattern at the position where the number of mismatches between each dot of the master pattern and the imaged pattern is the smallest.

The matching degree calculating means 13 calculates the pattern matching degree based on the degree of matching of both the black dots and the white dots.

[0013]

[Operation] In the present invention, the matching determining unit 11 determines the position where the number of mismatches between each dot of the master pattern and the imaged pattern is the least, and the matching degree calculating means 12 and the matching degree calculating means 13 determine the position where the number of mismatches between the dots of the master pattern and the imaged pattern is the least. The degree of pattern matching is calculated by taking into account each degree of matching.

[0014] Therefore, if the imaging pattern consists of either black dots or white dots due to an abnormality in the imaging pattern, an imbalance will occur between the matching degree of black dots and the matching degree of white dots. In the invention, pattern matching can be determined based on the pattern matching degree obtained by averaging this imbalance.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a block diagram of one embodiment of the present invention. In the figure, the same components as in FIGS. 1 and 3 are denoted by the same reference numerals, and their explanations will be omitted. In FIG. 2, the matching circuit 20 has a black/white dot coincidence calculation circuit 28 corresponding to the coincidence calculation means 12. Further, a matching degree calculation circuit 29 corresponding to the matching degree calculation means 13 is provided outside the matching circuit 20.

Next, the operation of this embodiment will be explained. Based on the master pattern from the memory 23 and the comparison pattern of the matching screen from the memory 24, the matching judgment section 27 uses the same method as the conventional matching judgment section 25 to determine the smallest number of mismatches between each dot of both patterns. ,
Find the position of the matching screen. The black/white dot coincidence degree calculation circuit 28 calculates, at the position where the number of mismatches is the smallest,
The degree of matching is calculated for each of the black dots and white dots of the master pattern and comparison pattern based on the following equation.

Matching degree of black dots = {(number of black dots in master pattern) - (unmatched black dots)


(number of black dots in master pattern)}/(number of black dots in master pattern) (
1) Matching degree of white dots = {(number of white dots in master pattern) - (unmatched white dots)


(number of white dots in master pattern)}/(number of white dots in master pattern)
(2) The black dot matching degree and the white dot matching degree calculated in this way are supplied to the matching degree calculating circuit 29, which calculates the matching degree based on the following equation.

(Degree of matching) = {(Degree of matching of black dots)
+ (matching degree of white dots)}


×100÷2(%)

(3) When the degree of matching (that is, the degree of matching) is equal to or greater than a predetermined threshold value greater than 50%, it is determined that pattern matching has been achieved.

Next, a specific example will be explained. Now, the master pattern is a pattern with black dots at diagonal positions among 8×4 dots as shown in FIG. 5(A), and on the other hand,
Assume that the comparison pattern is such that all 8×4 dots are white dots as shown in FIG. 5(B). In this case, the black/white dot coincidence calculation circuit 28 obtains the following equations (4) and (5) based on equations (1) and (2).

[0020]

[Math 1]

Thereby, the matching degree calculation circuit 29 calculates the degree of matching based on the above equation (3). Therefore, the matching degree (matching degree) is (
Matching degree)=(0+1)×100÷2=50(%)
(6) becomes.

Note that the degree of matching is also 50% when all the comparison patterns are black dots. Also, when the comparison pattern is the same as the master pattern, the matching degree is 1.
00%, and when the comparison pattern is a pattern that is black and white opposite to the master pattern, the matching degree is 0%. Therefore, in view of the above points, if the threshold value for determining whether a pattern has been established is, for example, 80%, then the matching degree shown in equation (6) is 50%.
%, it can be accurately determined that pattern matching cannot be achieved.

The matching degree calculating circuit 29 may be provided within the matching circuit 20, or the black/white dot matching degree calculating circuit 28 may be provided outside the matching circuit 20. In addition, the calculation of the matching degree of the present invention is (3)
It is not limited to the formula, but the point is that it is sufficient to obtain a value that comprehensively takes into account the degree of coincidence of black dots and white dots.

[0024]

As described above, according to the present invention, pattern matching is determined based on the degree of pattern matching that comprehensively takes into account the degree of coincidence of black dots and the degree of coincidence of white dots. It has features such as being able to perform sophisticated pattern matching.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle configuration of the present invention.

FIG. 2 is a block diagram of one embodiment of the invention.

FIG. 3 is a block diagram of a conventional example.

FIG. 4 is an explanatory diagram of a master pattern and a matching screen.

FIG. 5 is an explanatory diagram of a master pattern and a comparison pattern.

FIG. 6 is a diagram illustrating matching determination on a matching screen.

[Explanation of symbols]

11, 29 Matching judgment section 12 Matching degree calculation means 13 Matching degree calculation means 28 Black/white dot coincidence calculation circuit 29 Matching degree calculation circuit

Claims (2)

[Claims] 1. A master pattern that is the same as a combination pattern of black dots and white dots formed in advance on the sample;
A matching determination unit (11) that compares an imaged pattern obtained by imaging a part of the sample with an imaging device and determines a position where the number of mismatches between each dot of both patterns is the least.
, the degree of coincidence between the black dots in the master pattern and the black dots in the imaged pattern at a position where the number of mismatches between each dot of both patterns is the smallest, and the white dots in the master pattern and the imaged pattern. Matching degree calculation means (12
), and a matching degree calculating means (13) for calculating a pattern matching degree based on the degree of matching of both black dots and white dots calculated by the matching degree calculating means (12). matching device. 2. The matching degree calculating means (13) calculates a value obtained by dividing the sum of the matching degree of the black dots and the matching degree of the white dots by a predetermined value as the matching degree. 1. The pattern matching device according to 1.