JPH0374822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern defect inspection apparatus, and more particularly to a pattern determination method used in a reticle pattern defect inspection apparatus used in the manufacture of semiconductor integrated circuits.

Conventionally, in order to inspect defects in a reticle pattern created by placing a mask in close contact with a silicon wafer and photo-etching it, the applicant has proposed, in Japanese Patent Application No. 56-144740, PG (Pattern) to use
We are developing a device that can perform highly reliable defect inspection by comparing the information stored on a (Generation) tape with the actual pattern produced based on this tape.

In the above-mentioned apparatus, the pattern is divided from the PG tape into patterns for each unit scanning area (1 mm x 1 mm), and is stored as a set of rectangular elements in the reticle tape for each unit scanning area.For example, the pattern is curved. The parts are made by overlapping rectangular elements. Therefore, when overlapping patterns are stored on the reticle tape as shown in Figure 1, the rectangular pattern points (x ₂ , y ₁ ) and the rectangular pattern points (x ₃ , y ₁ ) are stored as a single point. In the case of patterns, all you had to remember was that it was a boundary point from white to black or from black to white, but when patterns overlap like this, it becomes a boundary point depending on the degree of overlap. The content of each pixel must be determined and stored on a separate reticle tape, and from that information it must be determined whether each pixel in the image is part of a pattern or not, that is, black or white. Ta. The above-mentioned work is extremely time-consuming and has the disadvantage of requiring an enormous amount of reticle tape.

The purpose of the present invention is to solve the above-mentioned problems, and to provide a pattern for use in a pattern defect inspection device that can easily and inexpensively fill in patterns by using a reticle tape with only a single rectangular data even in areas where patterns overlap. The purpose of this paper is to provide a method for determining the

In the pattern determination method of the present invention, a defect in a pattern of an object to be inspected, in particular a defect in a pattern of a mask used for manufacturing semiconductor integrated circuits, is determined based on a standard that is read out from a recording medium storing reference information corresponding to the pattern of the object to be inspected. In a defect inspection method that automatically detects defects by comparing information with scanning information obtained by actually scanning the pattern of the object, when determining the pattern portion represented by black in the binarized image, Pixels that exist on the border and change from white to black are +1, pixels that change from black to white are -1, and pixels that do not change are set as 0.The sum is calculated sequentially for each line and is the subject of judgment. This is characterized in that when the sum of the pixel values is 0, it is judged as white, and when it is other than 0, it is judged as black, that is, as a pattern part.

The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram showing the overall structure of a pattern defect inspection apparatus that implements the pattern determination method of the present invention. The overall configuration can be roughly divided into stage unit 10 and video signal conversion unit 3.
0 and a control unit 40. The operation of each part will be briefly explained below in the order described above.

First, in the stage unit 10, a pattern (for example, a reticle pattern, etc.) of a subject 18 is irradiated with light from a light source 11, and the transmitted light is incident on an image sensor 23 consisting of a bit array to obtain scanning data for one line. After that, the scanning data is output to the control section 40. Automatic focus mechanism 1
The objective lens 17 with lens 4 is used to magnify the transmitted light by a factor of 25, for example, and project it onto the bit array of the image sensor 23. The automatic focusing mechanism used in this example is
This mechanism is the same as that proposed in Publication No. 31348.
Selection and scanning of the scanning area are performed using the X table 15 and the Y table.
This is executed by driving the table 16 by the drive mechanisms 13 and 12. X, Y table 15,
16 is controlled by detecting their movements with linear encoders 19 and 20 and supplying them to a stage position collector 21. Here, the deviation in the X and Y directions is detected, and a correction signal obtained from the deviation is sent to the drive mechanisms 13 and 12.
correction is performed. In addition, since there is a problem in terms of accuracy with only this correction, especially in the X direction, the stage position collector 21
A correction signal is supplied to the image sensor driver 22 for the amount of deviation in the X direction from to obtain scanning data at 1000 points.

Next, the video conversion unit 30 in FIG. 2 will be explained. Created using CAD system etc.
The PG tape is converted into an inspection reticle tape 31 having the format of this system and supplied to a video conversion unit. This reticle tape 3
1 is attached to the tape unit 32, and then
Under the control of the CPU in the control unit 40, the file corresponding to the reticle mask 18 being inspected on the stage section 10 is read out from the reticle tape 31 via the magnetic tape control section 36, and is read out from the reticle tape 31 via the magnetic tape control section 36. Memorize to one side. Based on the coordinate group of points from the reticle tape 31 stored in the magnetic tape memory, the video signal converter 35 converts the coordinates into an image under the control of the synchronization signal from the magnetic tape controller 36, and then
The video is stored in one of two video memories. In the video signal converting section 35, the signal converted into a video signal is converted into a pattern image at a higher speed than the conventional method using a pattern determination method of the present invention which will be described later. The data created by the video signal converter 35 is read out by the video signal converter 35 corresponding to the portion scanned by the image sensor 23 of the stage section 10 under the control of the magnetic tape controller 36, The signal is output to the device 45.

Both outputs from the stage unit 10 and video conversion unit 30 created as described above are as follows.
It is supplied to the control unit 40. Control unit 4
0, both output signals are compared by a comparator 45 in order to detect the defective portion.

A signal after the comparison operation has been completed via the comparator 45 is supplied to a data processing section 47, where various processing is performed. The data processing section 47 is composed of various I/O interfaces, PAM, POM, CPU, and display section, and the processed data is outputted from the printer 48. Furthermore, each image is displayed on the monitors 41 to 44, and the processing can be checked.

FIG. 3 is a block diagram showing an embodiment of a video signal converter that implements the pattern determination method of the present invention. In Figure 3, magnetic tape memory 3
The reticle tape pattern information stored in 3 and 34 is converted into a video image by an image processor 50. At this time, if black is the pattern part in the binarized image, the pattern determines whether the pixel is a boundary pixel, that is, a pixel that changes from white to black, a pixel that changes from black to white, or a pixel that does not change at the same time as conversion. Read information. The switch 51 is switched based on the pattern information, and if the pixel is a boundary pixel that changes from white to black, it is stored as "1" in the corresponding position in the ON frame memory 52, and the pixel changes from black to white. If the pixel is a boundary pixel that changes to OFF, it is stored as "1" in the corresponding position in the frame memory 53 for OFF, and if the pixel is not a boundary pixel and does not change, it is stored in both frame memories 5.
Nothing is stored in the corresponding position in 2 and 53, and the state is kept at "0".

When the above-mentioned operations are completed for one image area, images in which only the boundary pixels that change from white to black are "1" and the other pixels are "0" can be obtained in the frame memories 52 and 53, respectively. . At this time, when boundary pixels of different patterns overlap, the boundary pixels of the pattern to be written later are written at positions shifted inward by one pixel.

Next, the corresponding lines in the frame memories 52 and 53 are read simultaneously, and the output of the frame memory 52 for ON is sent to the (+) terminal of the up-down counter 54, and the output of the frame memory 53 for OFF is sent to the (+) terminal of the up-down counter 54. (-) terminal to obtain up-down information for each pixel.
This up-down information is further transmitted to the zero detection circuit 55.
When the up-down information of the target pixel is 0, it is determined to be white, and when it is other than 0, it is determined to be black, that is, a pattern part. By performing this operation on all pixels in one image area, reference information can be obtained.

The above-described determination method will be explained using an actual example in which the rectangular patterns shown in FIG. 1 overlap.
If the target line is the straight line in FIG. 1, there is no pattern up to pixel (x ₁ , y ₁ ), so "0" is stored in the corresponding pixels in both frame memories 52 and 53. Pixel (x ₁ , y ₁ ) is a boundary pixel where the pattern changes from white to black, so
“1” is stored in the corresponding pixel in frame memory 52, and “0” is stored in frame memory 53. Since pixels (x ₁ , y ₁ ) to (x ₃ , y ₁ ) are not pattern boundary pixels, "0" is stored in both frame memories 52 and 53. Similarly, pixels (x ₂ , y ₁ ) and (x ₄ , y ₁ ) are boundary pixels that change from black to white, so "1" is stored in the corresponding pixels in the frame memory 53, and "1" is stored in the frame memory 52. 0” is stored. The pattern information thus stored in the frame memories 52 and 53 is separately supplied to the (+) and (-) terminals of the up-down counter 54 to obtain up-down information.
In this case, the up-down information is 0 from pixel (x ₁ , y ₁ ), 2 from pixel (x ₁ , y ₁ ) to (x ₂ , y ₁ ),
1 from pixel (x ₂ , y ₁ ) to (x ₄ , y ₁ ) to (x ₃ , y ₁ ), 1 from pixel (x ₃ , y ₁ ), and 1 from pixel (x 4 , y 1 ) to pixel (x ₄ , y 1 )
y ₁ ) to the last pixel of this line is 0.
Therefore, this up-down information is supplied to the zero check circuit 55, and it is determined that the area from the first pixel to the pixel (x ₁ , y ₁ ) and from the pixel (x ₄ , y ₁ ) to the final pixel is "0", that is, a part where no pattern exists. Pixel (x ₁ ,
A reference signal can be obtained by determining that the area from y ₁ ) to (x ₄ , y ₁ ) is "1", that is, a portion where a pattern exists.

FIG. 4 is a block diagram showing another embodiment of a video converter that implements the pattern determination method of the present invention. This embodiment is characterized in that reference information is obtained by processing the overlapping portions of the pattern boundaries as they are. That is, three up-counting frame memories 62, 63, and 64 are provided, and the overlap of boundary pixels in the image converted to a video image by the image processor 60 is determined by Stored as “1” in the corresponding position in frame memory (1) 62, and the number of overlapped pieces is 3.
When there are 4 pieces, "1" is stored in the corresponding position in frame memory (2) 63, and when the number of overlapped pieces is 4, "1" is stored in the corresponding position in frame memory (1) 62 and (2) 63, respectively. If there are 5 pieces, they are stored in the frame memory (4) 64 in the same way.
Thereafter, pattern information is obtained by storing up to eight overlapping pieces in the frame memories 62, 63, and 64 using the method described above. The pattern information stored in these frame memories 62, 63, and 64 is sequentially weighted with 1, 2, and 4 for each same pixel and is supplied to an adder 65 to obtain up count information. Frame memories 72, 73, and 74 having similar configurations are provided, and down count information is obtained in the same manner, and this up and down count information is processed by an up-down counter 66 and a zero detection circuit 67 in the same manner as in the embodiment described above. Standard information has been obtained.

As is clear from the detailed explanation above, according to the pattern determination method used in the pattern defect inspection apparatus of the present invention, pattern portions can be easily determined when obtaining reference information even in overlapping patterns. At the same time, the amount of pattern information stored on the reticle tape can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a state in which rectangular patterns overlap, FIG. 2 is a block diagram showing the overall configuration of a pattern defect inspection apparatus that implements the pattern determination method of the present invention, and FIG. 3 is a diagram showing the present invention. FIG. 4 is a block diagram showing one embodiment of a video converting section that implements the pattern determining method of the present invention. FIG. 4 is a block diagram showing another embodiment of the video converting section that implements the pattern determining method of the present invention. 10...Stage unit, 30...Video signal conversion unit, 40...Control unit, 50,
60... Image processor, 51, 61... Switch,
52, 53, 62, 63, 64, 72, 73, 7
4... Frame memory, 54, 66... Up-down counter, 65, 75... Adder, 5
5,67...Zero detected.

Claims (1)

[Scope of Claims] 1. Defects in the pattern of an object to be inspected, particularly defects in the pattern of a mask used in the manufacture of semiconductor integrated circuits, can be detected using reference information read from a recording medium that stores reference information corresponding to the pattern of the object to be inspected. In a defect inspection method that automatically detects a pattern by comparing it with scanning information obtained by actually scanning a pattern of the object,
When determining the pattern portion represented by black in a binarized image, pixels that exist at the boundary of the pattern and change from white to black are set as +1, pixels that change from black to white as -1, and pixels that do not change as 0. A pattern defect inspection characterized in that the sum is sequentially determined for each line, and when the sum in the pixel to be judged is 0, it is judged to be white, and when it is other than 0, it is judged to be black, that is, a pattern part. A method for determining patterns used in devices. 2. Used in the pattern defect inspection apparatus according to claim 1, characterized in that when the boundary pixels of the patterns overlap, the boundary pixels of the pattern to be written later are written at positions shifted inward by one pixel. How to judge patterns. 3 Using a multi-sided memory consisting of a three-sided frame memory with an addition function, the degree of overlapping of patterns on each side is defined, and when storing each boundary pixel, a plane is created for each boundary pixel according to the number of times the pattern overlaps. 2. A pattern determination method for use in a pattern defect inspection apparatus according to claim 1, characterized in that the pattern is stored only in the memory, and read out after being weighted for each memory.