KR100675890B1 - Method for inspecting the defects of semiconductor device - Google Patents

Abstract

Defect detection method of a semiconductor device of the present invention comprises the steps of preparing a wafer on which the inspection target comparison patterns are formed; Irradiating light onto the wafer to detect reflected / scattered light to obtain a gray level for each of the comparison patterns; Setting defect detection reference values for the comparison patterns for each wafer position; And comparing the defective detection reference value with the gray level of the comparison patterns one-to-one to determine whether the pattern is defective.

Gray level, bad detection reference value

Description

Method for inspecting the defects of semiconductor device

1 is a view illustrating a method for inspecting a defect of a semiconductor device.

2A to 2D are views illustrating a defect detection method and a problem of a semiconductor device using an optical inspection apparatus according to the prior art.

3 and 4 are flowcharts illustrating the defect detection method of the semiconductor device according to the embodiment of the present invention.

5A to 5D are SEM images shown to specifically explain the steps of FIGS. 3 and 4.

<Explanation of symbols for the main parts of the drawings>

40: first comparison pattern 42: second comparison pattern

44: third comparison pattern 46: fourth comparison pattern

48 pixels

The present invention relates to a defect detection method of a semiconductor device, and more particularly, to a method of detecting a defect of a semiconductor device using an optical inspection equipment.

In general, a method of inspecting a defect of a semiconductor device includes a bright field method using an amount of light reflected directly from a specific part of a semiconductor device to be inspected, and by illuminating a specific part of the semiconductor device to be inspected. There is a dark field method that uses the amount of light scattered. In order to inspect the defect of the semiconductor device, one of these methods is selected and the amount of light, that is, the number of photons, is reflected or scattered from the semiconductor device and reaches the sensor of the optical inspection equipment.

The method of checking the amount of light reaching the sensor is to divide the amount of reflected or scattered light into a certain section to determine the gray level for each pixel, the minimum area of comparison of the scan area. After assigning, the gray levels of adjacent areas are compared with each other, and when the difference is larger than the threshold value of detection, the defect is recognized as a defect.

1 is a view illustrating a method for inspecting a defect of a semiconductor device.

Referring to FIG. 1, the left side shows an image of the reference inspection area 100, and the center shows an inspection area 102 compared adjacent thereto. If there is a difference 106 as in the inspection region 104 on the right side, compared with the image of the reference inspection region 100 on the left side by examining the amount of light reflected or scattered by shining light onto the semiconductor substrate, You can judge. In this case, the inspection regions 100, 102, and 104 include a plurality of pixels 101. At this time, the gray level is set according to the amount of light reflected from the pixel 101. For example, the darkest case 108 may be displayed as 0 and the brightest case 110 may be represented as 255. The gray region 112 may be represented as 1 to 254 according to the degree of black and white contrast. Can be. Therefore, when the image of the inspection area 102 is compared with the reference image 100 and the difference value is larger than a predetermined defective detection reference value, the corresponding pixel 114 is recognized as a defect.

However, this comparison test method recognizes that a certain amount of difference must occur in comparison with the corresponding pixel of the next-repeated pattern, and it is recognized as a defect. Becomes difficult.

2A to 2D are diagrams illustrating a defect detection method and a problem of a semiconductor device according to the prior art.

2A to 2D, in the conventional defect detection method, the gray levels 10, 20, 30, and 40 are first applied to each pixel of the comparison pattern, and the gray level is detected to some extent in comparison with the adjacent comparison pattern. It is recognized as a defective part when it is equal to or more than the reference value, but when the difference between adjacent comparison patterns is insignificant, defect detection becomes difficult. In this case, the comparison pattern may be formed to include the pixel 28 which is the minimum comparison area. Also, the patterns of FIGS. 2A to 2D may be comparison patterns adjacent to each other.

For example, when the defect detection reference value is 20, the difference between 10 which is the gray level of the first comparison pattern 20 and 20 which is the gray level of the second comparison pattern 22 is 10. Next, a difference value of 30, which is the gray level of the third comparison pattern 24 which is the comparison pattern adjacent to the gray level of the second comparison pattern 22, becomes 10, and the comparison that is adjacent to the third comparison pattern 24 is performed. The difference value of 40 which is the gray level of the 4th comparative pattern 26 which is a pattern becomes 10. FIG.

Then, the difference value between the adjacent comparison patterns is represented by 10, respectively, and becomes less than or equal to 20, which is a defective detection reference value, so that there is no defective portion. However, when comparing the gray levels defined for the pixels 28, minute differences occur from the first comparison pattern 20 to the fourth comparison pattern 26, and these differences accumulate to affect the performance of the wafer. . That is, although the gray level difference of the pixels of the same part compared between the pixels of the comparison pattern is small and is not detected as a defect, when the slight difference of gray level is applied equally and passes several repeated comparison patterns, the first comparison pattern The difference in gray levels between the pixel which is the smallest unit in (20) and the pixel which is the smallest unit in the final comparison pattern 26 is increased by twice the number of repeated comparison patterns beyond the comparison difference value of the first adjacent pattern.

In addition, there is a change in process margin, so that the pattern formation process is performed after a process such as defect inspection and chemical mechanical polishing of wafers with a large pattern change but a small pattern change locally. In the case of wafers and similarly inspected wafer defects of a photo polished matrix, a problem in which a defect detection possibility becomes very low by a conventional defect detection method occurs.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a method for detecting a defect in a semiconductor device, which improves a method for detecting a defect when the defect detection method for a semiconductor device according to the prior art recognizes the defect only when the defect is detected.

In order to achieve the above technical problem, a failure detection method of a semiconductor device according to the present invention comprises the steps of preparing a wafer on which the inspection target comparison patterns are formed; Irradiating light onto the wafer to detect reflected / scattered light to obtain a gray level for each of the comparison patterns; Setting defect detection reference values for the comparison patterns for each wafer position; And comparing the defective detection reference value with the gray level of the comparison patterns one-to-one to determine whether the comparison pattern is defective.

In the present invention, when the gray level of the comparison pattern is equal to or more than the defective detection reference value, it is recognized as a defective.

In order to achieve the above technical problem, a failure detection method of a semiconductor device according to the present invention, preparing a wafer on which the inspection target comparison patterns are formed; Irradiating light onto the wafer to detect reflected / scattered light to obtain a gray level for each of the comparison patterns; Setting defect detection reference values for the comparison patterns for each wafer position; And comparing the average value of the gray levels with respect to the comparison patterns in the predetermined region and the defective detection reference value to determine whether the defect is in the region.

In the case where the gray level is greater than or equal to the average value of the gray levels for the comparison patterns in the predetermined region, the gray level is recognized as defective.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification.

3 and 4 are flowcharts illustrating a failure detection method of a semiconductor device in accordance with an embodiment of the present invention. 5A through 5D are SEM images shown to specifically describe the steps of FIGS. 3 and 4.

Referring to FIGS. 3 and 4, first, loading is performed into inspection equipment in order to detect a failure of a semiconductor substrate which has been subjected to a predetermined process (step 300 and step 400). Next, light is irradiated onto the surface of the semiconductor substrate in order to detect defects from the surface of the semiconductor substrate. The surface of the semiconductor substrate may be formed to include the pixel 48 (see FIG. 5), which is a minimum comparison region having the same pattern. Here, the light irradiated onto the surface of the substrate is preferable to use short wavelength light so as to have excellent reflection performance and to reduce the possibility of interference on the surface of the semiconductor substrate. The gray level is provided according to the amount of light reflected from the surface of the semiconductor substrate with respect to each comparison pattern (step 310 and step 410).

Next, a defect detection reference value, which is a criterion for determining whether a defect is determined, is set by comparing with the gray level applied to each comparison pattern (step 320 and step 420).

Next, the defect detection reference value is compared with the first comparison pattern (step 330 and step 430). Here, as a method of comparing the defect detection reference value and the comparison pattern, a method of comparing the defect detection reference value and the gray level itself of the comparison pattern may be used. (Refer to FIG. 3) When the gray level of each comparison pattern is larger than the bad detection reference value and the gray level of the comparison pattern, the comparison pattern can be recognized as a bad pattern (steps 340 and 350). .

In this case, as a method of comparing the defective detection reference value and the first comparison pattern, a method of comparing the gray level average value and the defective detection reference value of the comparison pattern at the same position may be used (see FIG. 4). If the value has a value larger than the defective detection reference value, the comparison pattern can be recognized as a defective pattern (steps 440 and 450).

5A to 5D, when the gray level itself of the comparison pattern is compared with the defective detection reference value, the gray levels 10, 20, 30, and 40 are first given to each of the comparison patterns, and the defective detection reference value is, for example, 25. After giving it to and compare with the gray level of the comparison pattern. Then, the first comparison pattern 40 and the second comparison pattern 42 having gray levels lower than 25 are recognized as normal, and the third comparison pattern 44 and the fourth comparison pattern having gray levels higher than 25 are normal. 46 is recognized as a bad pixel.

In addition, the method of comparing the defect detection reference value and the comparison pattern may also use a method of recognizing a comparison pattern that is a certain value or more than the average value of each of the comparison patterns 40, 42, 44, and 46 as a failure pattern. For example, when a value equal to or greater than 3 is given as a defective detection reference value for recognizing a defective value, the average gray level value of the first comparison pattern 40 to the fourth comparison pattern 46 is (10 + 20 +). 30 + 40) / 4 = 25. If the value of 3 or more than the average value of 25 is recognized as defective, the gray levels of the third comparison pattern 44 and the fourth comparison pattern 46 become 30 and 40, respectively, and thus may be recognized as defective.

Here, the method of comparing the gray level itself of the comparison pattern with the defect detection reference value can be used when checking the margin of the wafer or measuring the pattern accuracy, and the method using the average value can be used when checking only the serious defect degree. In addition, when comparing the gray level of the defective detection reference value and the comparison pattern, in addition to the above-described methods, it is possible to detect the defective pixels by using function values such as the median value, standard deviation value, maximum value and minimum value of the comparison pattern in the same position. It may be.

If this process is performed until the defect detection reference value is satisfied by comparing the gray levels of all the comparison patterns on the wafer (steps 360 and 460), the semiconductor substrate is unloaded from the optical inspection equipment (steps 380 and 480) and ends. do.

According to an embodiment of the present invention, the gray level itself of the comparison pattern is compared with the defect detection reference value or the average value is used, even if the difference between adjacent patterns is inferior. The margin of detection is very low in the conventional defect detection method. It can proceed more easily than the defect inspection of the related pattern wafer inspection.

As described so far, according to the defect detection method of the semiconductor element according to the present invention, even if the difference between adjacent patterns is insignificant, the defect can be recognized, and the formation degree or the defect degree of the pattern in the wafer can be detected more easily.

Claims (4)

Preparing a wafer on which inspection target comparison patterns are formed; Irradiating light onto the wafer to detect reflected / scattered light to obtain a gray level for each of the comparison patterns; Setting a defective detection reference value numerically based on gray levels for the comparison patterns for each wafer position; And determining whether the comparison pattern is defective by comparing the defect detection reference value with the gray level of the comparison patterns in a one-to-one manner. The method of claim 1, If the gray level of the comparison pattern is equal to or greater than the defect detection reference value, it is recognized as a failure. Preparing a wafer on which inspection target comparison patterns are formed; Irradiating light onto the wafer to detect reflected / scattered light to obtain a gray level for each of the comparison patterns; Setting a defective detection reference value numerically based on gray levels for the comparison patterns for each wafer position; And comparing the failure detection reference value with an average value of gray levels with respect to the comparison patterns in a predetermined region to determine whether the defect is in the region. The method of claim 1, The method for detecting a defect of a semiconductor device according to claim 1, wherein when the gray level is 3 or more than an average value of the gray levels of the comparison patterns in the predetermined region, the defect is recognized as a defect.

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