JPH07128248A - Defect inspection device - Google Patents

Abstract

PURPOSE:To mutually compare the areas and positions of contact holes on design information and a material to be inspected, and precisely detect the minimize defect or displacement defect of the contact hole pattern. CONSTITUTION:In a defect inspection device having a subject 2 to be inspected placed on a moving stage 1, an image pickup device 3, a multi-valuing circuit 4, a computing element 5, a memory circuit 8, a bit expanding circuit 10, area measuring circuits 11, 12, a comparing circuit 13 and a defect information memory circuit 14, design data is converted into multi-valued data by the bit expanding circuit 10, and inputted to the area measuring circuit 11, and the subject data taken by the image pickup device 3 is converted into multi-valued data by a multi-valuing circuit 4, and inputted to the area measuring circuit 12. In the area measuring circuits 11, 12, the areas of the subject multi-valued data and the design multi-valued data are measured with a window as an unit. In the comparing circuit 13, the areas measured by the area measuring circuits 11, 12 are mutually compared in the same position. The comparison result is stored in the defect information memory circuit 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus using a pattern recognition technique, and in particular, it can be obtained from a geometrical inspection pattern manufactured based on design information and its design information. The present invention relates to a defect inspection apparatus that detects a defect in a pattern to be inspected by comparing it with a design pattern.

[0002]

2. Description of the Related Art As a conventional defect inspection apparatus for detecting a defect of a mask pattern, a reticle pattern, etc., for example, the following is known. The device disclosed in Japanese Patent Laid-Open No. 62-280981 detects the size of the pattern defect by directly comparing the pattern to be inspected with the design pattern except for the edge portion of the pattern. The apparatus disclosed in Japanese Patent Laid-Open No. 62-212546 detects a pattern defect by detecting and comparing characteristic patterns such as corners and steps of the pattern with respect to both the pattern to be inspected and the design pattern. To do. JP-A-4-26402 and JP-A-4-356.
The apparatus described in Japanese Patent Publication No. 84 detects the defect of the pattern by comparing the dimensions of the pattern to be inspected and the design pattern in a plurality of directions by a length measuring sensor that measures the dimension of the pattern.

[0003]

However, with regard to the missize defect and the position shift defect of the contact hole pattern which is formed for the purpose of conducting each pattern surface composed of a plurality of layers, the defect in the above-mentioned defect inspection device is not satisfied. May be overlooked. That is, in the device of (1), if the defect occurs in the edge portion, it is ignored as a non-comparison target. In the above device, if the generated defect does not appear as a difference in a corner or a step, it cannot be detected.
Since the device of (1) is mainly intended to detect a defect of the wiring pattern width, even if there is a defect in a minute pattern such as a contact hole pattern, if the wiring pattern width is normal, the defect may be overlooked. is there.

If the formation position of the contact hole pattern, which is a minute pattern, is deviated, it becomes impossible to electrically connect the pattern surfaces of a plurality of layers. Further, when the area of the contact hole pattern is equal to or smaller than the design value, disconnection is likely to occur in the contact hole portion and the pattern resistance value may increase. Therefore, the area error of the contact hole pattern greatly determines the quality of the pattern. It becomes an element.

It is an object of the present invention to measure the area and position of contact hole patterns of both design pattern data and inspected pattern data and compare them to accurately detect missize defects and misalignment defects of the contact hole patterns. It is to provide a defect inspection device capable of detecting.

[0006]

The present invention will be described with reference to FIG. 1 showing an embodiment. The present invention is designed pattern data output means 10 for outputting design pattern data based on design information, and design information. The pattern to be inspected formed on the object to be inspected on the basis of the image to be inspected, and the pattern data output means 4 for outputting the pattern data to be inspected are compared with the design pattern data and the pattern data to be inspected. It is applied to a defect inspection apparatus provided with a defect detection unit 13 for detecting a defect in the above pattern, a reference pattern measuring unit 11 for extracting a contact hole pattern from design pattern data, and measuring its area and position, and a target pattern measuring unit 11. A pattern to be inspected 12 for extracting the contact hole pattern from the inspection pattern data and measuring the area and position thereof. The defect detecting means 13 detects the defect of the pattern on the inspection object by comparing the area and the position of the contact hole pattern measured by the reference pattern measuring means 11 and the inspection pattern measuring means 12, respectively. By configuring, the above-mentioned object is achieved.

According to a second aspect of the invention, in the defect inspection apparatus according to the first aspect, the reference pattern measuring means 1 is used.
1 and the inspected pattern measuring means 12 are configured to estimate the area of the contact hole pattern based on each pattern width measured by at least two line segments intersecting the contact hole pattern.
According to a third aspect of the present invention, in the defect inspection apparatus according to the first aspect, the reference pattern measuring unit 11 and the inspected pattern measuring unit 12 are set to a sum of luminance values for each pixel unit included in the contact hole pattern. The area is estimated based on this.

[0008]

According to the first aspect of the invention, the area and position of the contact hole pattern in the design pattern data extracted by the reference pattern measuring means 11 and the inspected pattern data extracted by the inspected pattern measuring means 12 The area and the position of the contact hole pattern are compared by the defect detecting means 13.

Incidentally, in the section of means and action for solving the above-mentioned problems for explaining the constitution of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. It is not limited to.

[0010]

1 is a block diagram of an embodiment of the defect inspection apparatus according to the present invention, and the main purpose of this embodiment is to detect defects in a contact hole pattern as shown in FIGS. . FIG. 2 shows a mask pattern used for semiconductor manufacturing. The shaded portion in the figure is a portion formed of chrome or the like that does not transmit light (hereinafter referred to as a light shielding portion), and the white portion is a portion that transmits light (hereinafter , And the white portion corresponds to the contact hole position (hereinafter, the pattern of the white portion is referred to as a contact hole pattern).
Contrary to FIG. 2, depending on the mask pattern, the contact hole pattern may be formed by the light-shielding portion, but the case where the contact hole pattern is formed by the transmitting portion will be described below.

FIG. 3 is a diagram showing an example of a defect in a contact hole pattern. The hatched portion in the figure shows the shape of a mask pattern (hereinafter referred to as a pattern to be inspected) actually formed, and the dotted portion shows the original contact. Hall pattern (hereinafter,
(Referred to as a reference pattern). 3A shows a case where the inspection pattern has no defect, FIG. 3B shows a case where the contact hole pattern in the inspection pattern is smaller than the reference pattern, and FIG. 3C shows a contact hole pattern in the inspection pattern which is smaller than the reference pattern. When it is larger, (d) shows the case where the lower side of the contact hole pattern in the pattern to be inspected is smaller than the reference pattern, and (e) shows the case where the contact hole pattern and the reference pattern in the pattern to be inspected are misaligned.

In FIG. 1, reference numeral 1 is a moving stage for moving an object to be inspected 2 such as a reticle or a mask in one direction. An image pickup device 3 is arranged above the moving stage 1. The image pickup device 3 picks up an image of the inspection object pattern in a direction perpendicular to the moving direction of the substrate and outputs an analog image signal according to the luminance distribution. Reference numeral 4 is a multi-valued circuit that samples the analog image signal from the image pickup device 3 and multi-values it. The multi-value quantization circuit 4 samples 1024 times per scan of the image pickup device 3, converts each sampling result into a digital signal, and outputs 8
It is output as a multi-valued image signal of bits (hereinafter referred to as inspected multi-valued data). For example, as the imaging device 3, 1024
When a CCD line sensor having pixels is used and sampling is performed on a pixel-by-pixel basis, when the entire inspected object 2 is imaged, 1024 × N (N is a number that varies depending on the moving distance of the moving stage 1, the scanning interval of the image pickup device 3, etc.). ) Time-series image data for pixels is obtained. The multi-valued data to be inspected is, for example, "245" when imaging the transmission part and "10" when imaging the light shielding part.

Reference numeral 5 is a computer for reading design pattern data (having an accuracy of about 0.1 pixel) of the inspection object 2 stored in a magnetic tape (not shown) via the magnetic tape device 6. The computer 5 is composed of a CPU, a memory and the like, and divides the read design pattern data into small areas and stores them in the magnetic storage device 7. The above-described processing from the magnetic tape reading by the computer 5 to the storage in the magnetic recording device 7 is performed before the defect inspection. The design data in small area units stored in the magnetic storage device 7 is read by the computer 5 and stored in the storage circuit 8. The computer 5 also sends to the drive unit 9 a signal instructing the movement of the moving stage 1 on which the inspection object 2 is placed.

Reference numeral 10 is a bit expansion circuit for converting the design pattern data stored in the storage circuit 8 into 8-bit multivalued data. Bit-expanded multi-valued data (hereinafter,
The design multivalued data) is input to the area measuring circuit 11. The area measuring circuit 11 extracts the contact hole pattern included in the design multivalued data and measures the area.
Similarly, the area measuring circuit 12 extracts the contact hole pattern included in the inspected multi-valued data and measures the area thereof. Reference numeral 13 is a comparison circuit for detecting the defect in the contact hole pattern of the inspection object 2 by comparing the areas measured by the area measuring circuits 11 and 12 by aligning the positions. The defect information detected by the comparison circuit 13 is once stored in the defect information storage circuit 14 and then read by the computer 5.

Details of the structures of the area measuring circuits 11 and 12 will be described below. Since the structure of the area measuring circuit 11 is basically the same as that of the area measuring circuit 12, two kinds of structures of the area measuring circuit 12 will be described below.

-Structural Example 1-FIG. 4 is an enlarged view of a contact hole pattern. In this configuration example 1, the dimensions of the contact hole pattern are measured in the directions a, b, c, d4 shown in the figure (each direction differs by 45 degrees), and the area value of the contact hole pattern is approximated from these dimension values. Ask for. FIG. 5 is a block diagram of the area measuring circuit 12 of the configuration example 1. In FIG. 5, the input multivalued data is cut out by the cutout circuit 21 in units of windows. The size of this window depends on the size of the defect to be detected.
As shown in FIG. 6A, the image is cut out into a window having a size of 10 pixels vertically and 10 pixels horizontally.

Design multi-valued data cut out in units of windows are input to four dimension measuring circuits 22 to 25,
The pattern dimensions in each of the directions a to d shown in FIG. 4 are measured. The dimension measuring circuits 22 to 25 are shown in FIG.
As shown in (b) and (c), it is composed of ROMs 31 and 32. For example, the cut out window is shown in FIG.
In the case of (a) (the dotted line portion in the figure is a contact hole pattern), the address terminal of the ROM 31 in the dimension measuring circuit 22 for measuring the pattern dimension in the a direction of FIG. The multi-valued data at the six points indicated by the marks are input. As shown in the figure, these 6 locations are arranged in groups of 3 locations, and the spacing between the groups is approximately equal to the width of the contact hole pattern in the a direction. Therefore, the edge position of the pattern in the a direction of the contact hole pattern is obtained by detecting the multivalued data to be inspected at these 6 locations, and the pattern dimension value in the a direction is obtained from this edge position. The ROM 31 stores in advance the respective dimension values when the multi-valued data at these six locations have changed arbitrarily, and outputs the pattern dimension values according to the values input to the address terminals.

When the dimension value is obtained for one window, the clipping circuit 21 shifts the window position by one pixel to obtain the dimension value again. In this way, the area measuring circuit 9 sequentially shifts the window position to obtain the dimension value of the contact hole pattern for each window position. As the window is shifted, the position of the contact hole pattern in the window relatively shifts, so that the edge of the contact hole pattern cannot be detected in at least one of the two sets in FIG. 6A. In such a case, there is no valid data and the dimension value “0” is output. The dimensions of the pattern measured in four directions in this way are:
The valid data which is input to the ROM 22 provided for each direction and whose value is not “0” is selected as the dimension value in that direction. If there are a plurality of contact hole patterns having different areas on the inspection object, RO
It suffices to prepare a plurality of M31 and input the inspected multi-valued data in which the intervals of the two sets in FIG. 6A are changed to each ROM 31.

When the number of address terminals of the ROM 31 is limited, of the six locations shown in FIG. 6 (a),
It is also possible to input only the multi-valued data at three points on one side to the ROM 31, measure the edge position of the pattern instead of measuring the dimension, and input the edge position to the ROM 32. By shifting the window, ROM32
Since the edge positions on both sides of the pattern are input to, the dimension of the pattern can be measured.

The dimension values in each direction measured by the dimension measuring circuits 22 to 25 shown in FIG. 3 are input to the conversion circuit 26, and the area of the contact hole pattern is obtained. The conversion circuit 26 is composed of, for example, a ROM, and the area value when the dimension value in each direction arbitrarily changes is stored in advance, and the area value corresponding to the input dimension value is output.

As described above, according to the configuration example 1, the contact hole pattern dimension is measured by using only a part of the multivalued data, and the area of the contact hole pattern is obtained based on the dimension value. Therefore, the pattern area can be accurately measured with a simple circuit configuration. Further, the areas of the inspected multi-valued data and the design multi-valued data are compared by shifting the windows by the same amount, so that the position of the contact hole pattern can be measured at the same time.

In the above configuration example 1, 8-bit multi-valued data at 6 locations is input to the address terminal of the ROM 31,
The number of multi-valued data to be detected is not limited to 6 places, and the number of bits of multi-valued data is not limited to 8 bits. In the above configuration example 1, the dimension measuring circuit is configured by the two ROMs 31 and 32, but it may be configured by one ROM or may be configured by being distributed to three or more ROMs. Or ROM
Instead of, a PLD (programmable logic device) may be used.

-Structural Example 2- In Structural Example 1, the area is obtained from the dimension value of the contact hole pattern, whereas in Structural Example 2, the pattern is obtained by calculating the sum of multi-valued data values of the contact hole pattern portion. The area is estimated. The output of the multi-value quantization circuit 4 in FIG. 1 is as shown in FIG. 7, for example. In FIG. 7, the part where "10" is written is a light shielding part, and the part where "245" is written is a transmissive part. When there is a contact hole pattern in the portion surrounded by the dotted line, the output of the multi-value quantization circuit 4 near the edge of the pattern is "1" as shown in the figure.
It takes an intermediate value between "0" and "245". This is because the light transmittance is low near the edges of the pattern.

FIG. 8 is a block diagram of the area measuring circuit 12 of the second configuration example. In FIG. 8, the input multivalued data to be inspected is cut out by the cutout circuit 41 in units of windows. The inspected multi-valued data (hereinafter referred to as cut-out data) in the cut out window is added to the horizontal addition circuit 42 to.
45 and the recognition circuit 46. Horizontal adder circuit 42-
At 45, the difference between the value of the cutout data and the inspected multi-valued data value of the light shielding portion is calculated. Here, the difference is calculated because the inspection object itself has variations in brightness, and the differences are absorbed by calculating the difference.
That is, when the object to be inspected is imaged, “245” is obtained as the multi-valued data value of the transmission part and “10” is obtained as the multi-valued data of the light-shielding part, and the former is “255”.
Since there are cases where “20” is obtained as the latter case, the difference in brightness is eliminated by calculating the difference between the former case and the latter case.

The horizontal adder circuits 42 to 45 are provided for the number of vertical lines of the window, and the horizontal adder circuits 42 to 4 are provided.
5 adds the above difference for each line. The number of horizontal adder circuits is determined by the size of the contact hole pattern and the size of the pixels of the image pickup device 3. Recognition circuit 46
Controls the output timing of the calculation result in the horizontal addition circuits 42 to 45 and the vertical addition circuit 47. This recognition circuit 46 determines whether or not there is a contact hole pattern in the window, and if there is a contact hole pattern, the addition result is sent to the vertical addition circuit 47 for each of the horizontal addition circuits 42 to 45. Instruct to send. In the vertical adder circuit 47, the calculation results of the horizontal adder circuits 42 to 45 are added, and the sum of multi-valued data values of the entire contact hole pattern is obtained. Then, this value is output as the area value.

As described above, in the configuration example 2, since the area value is obtained by adding the multi-valued data of all the pixels in the contact hole pattern, the area of the contact hole pattern can be measured more accurately than in the configuration example 1. it can. Further, the area measurement is performed in consideration of the fact that the light transmittance is lower in the vicinity of the edge of the pattern or in the pattern having a smaller area, so that the measurement accuracy is improved. Then, by performing such a measurement, it becomes possible to detect a defect in which the pattern shape is normal but the light transmittance is lower than usual.

If the comparison circuit 13 compares the patterns on the basis of the result of the configuration example 1 or 2 described above, FIG.
Not only defects such as those shown in (b), (c), and (d) whose areas are different from the design data can be detected, but also misalignment defects as shown in FIG. 3 (e) can be detected. That is, since the comparison circuit 13 compares the pattern data to be inspected with the design pattern data at the same window position, if there is a window at the dotted line position in FIG. There is a difference between the area value of the contact hole pattern and the area value in the pattern data to be inspected, so that it is detected that the inspected object has a displacement error.

On the other hand, when an image of the object 2 to be inspected is picked up by the image pickup device 3, a slight amount of position shift occurs due to the movement of the stage and the data acquisition shift of the image pickup device 3, so if the position shift detection is performed too strictly. However, even if there is no actual positional deviation, it may be erroneously recognized as a positional deviation. Therefore, as described in Japanese Unexamined Patent Publication (Kokai) No. 62-212546, when detecting the positional deviation,
The pattern information of the design pattern data may be enlarged and compared. Generally, the larger the amount of expanding the pattern information of the design pattern data, the lower the detection sensitivity of the misalignment defect, so depending on the required detection sensitivity,
The pattern information may be enlarged.

In the above embodiment, the area is measured after converting both the design pattern data and the pattern data to be inspected into multi-valued data, but the area may be measured by converting it into binary data. This makes it possible to detect defects with a simple circuit configuration although the accuracy is lowered.

In the embodiment configured as described above, the bit expanding circuit 10 serves as design pattern data output means, the multi-value quantization circuit 4 serves as inspected pattern data output means, and the comparison circuit 13 serves as defect detection means. The area measuring circuit 11 corresponds to the reference pattern measuring means, and the area measuring circuit 12 corresponds to the inspected pattern measuring means.

[0031]

As described in detail above, according to the present invention, the contact hole patterns are extracted from both the design pattern data and the pattern data to be inspected and their areas and positions are compared. It is possible to accurately detect missize defects and misalignment defects.
Further, according to the invention as set forth in claim 2, the area of the contact hole pattern is estimated based on each pattern width measured by at least two line segments intersecting the contact hole pattern, so that a simple circuit configuration is provided. Can detect defects with high accuracy. Further, according to the third aspect of the invention, the area value is obtained based on the sum of the brightness values in the contact hole pattern, so that the area of the contact hole pattern can be measured more accurately.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a defect inspection apparatus according to the present invention.

FIG. 2 is an outline view of a mask pattern including a contact hole pattern.

FIG. 3 is a diagram showing a defect example of a contact hole pattern.

FIG. 4 is an enlarged view of a contact hole pattern.

FIG. 5 is a block diagram of an area measuring circuit of configuration example 1;

FIG. 6 is a diagram showing a window.

FIG. 7 is a diagram showing an output of a multi-value quantization circuit.

FIG. 8 is a block diagram of an area measuring circuit of configuration example 2;

[Explanation of symbols]

 1 Moving Stage 2 Inspected Object 3 Imaging Device 4 Multi-valued Circuit 5 Computer 6 Magnetic Tape Device 7 Magnetic Storage Device 8 Storage Circuit 9 Drive Unit 10 Bit Development Circuit 11, 12 Area Measurement Circuit 13 Comparison Circuit 14 Defect Information Storage Circuit

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Claims (3)

[Claims] 1. A design pattern data output means for outputting design pattern data based on design information, and an image of a pattern to be inspected formed on an object to be inspected based on the design information to output the pattern data to be inspected. Inspected pattern data output means for, and a defect detection device comprising a defect detection means for comparing the design pattern data and the inspected pattern data to detect a defect in the pattern on the inspected object, wherein the design pattern A reference pattern measuring means for extracting a contact hole pattern from data and measuring its area and position; and an inspected pattern measuring means for extracting a contact hole pattern from the inspected pattern data and measuring its area and position. The defect detection means includes the reference pattern measurement means and the inspected pattern. By comparing the area and position of the contact hole pattern measured respectively by the measuring means, the defect inspection apparatus and detecting defects of a pattern on the object to be inspected. 2. The defect inspection apparatus according to claim 1, wherein the reference pattern measuring unit and the inspected pattern measuring unit measure each pattern by at least two line segments intersecting the contact hole pattern. A defect inspection apparatus, wherein the area of the contact hole pattern is estimated based on the width. 3. The defect inspection apparatus according to claim 1, wherein the reference pattern measuring unit and the inspected pattern measuring unit have an area based on a sum of luminance values for each pixel included in the contact hole pattern. A defect inspection apparatus characterized by estimating.