CN106971955B - Wafer defect detection method - Google Patents
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- CN106971955B CN106971955B CN201710353548.8A CN201710353548A CN106971955B CN 106971955 B CN106971955 B CN 106971955B CN 201710353548 A CN201710353548 A CN 201710353548A CN 106971955 B CN106971955 B CN 106971955B
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- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/10—Measuring as part of the manufacturing process
- H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
Abstract
The invention provides a method for detecting wafer defects, which comprises the following steps: acquiring an image of the surface of a wafer, and dividing the image of the surface of the wafer into a plurality of detection areas; selecting a plurality of first detection areas in each detection area, performing differentiation comparison on the first detection areas in each detection area, and obtaining a threshold value used for representing a defect of each detection area according to the result of the differentiation comparison; dividing each detection area into a plurality of second detection areas, comparing the difference of the second detection areas in each detection area with the threshold value of the corresponding detection area, and if the comparison result meets the preset condition, obtaining the defects existing in the corresponding detection area. According to the invention, different thresholds are set for different detection areas to obtain the number of defects corresponding to the different detection areas, so that more residual defects of the polycrystalline silicon are captured, and the detection accuracy is improved.
Description
Technical Field
The invention relates to the field of semiconductor manufacturing, in particular to a method for detecting wafer defects.
Background
In the field of semiconductor manufacturing, after a wafer is chemically and mechanically ground, the number of defects on the wafer needs to be scanned and determined so as to achieve the purpose of checking whether the process meets the requirements.
In actual production, the polishing head of the chemical mechanical polishing machine can optimize the flatness of the wafer by controlling different pressures to different areas of the wafer. In the process of grinding the wafer, the grinding head presses the wafer downwards and the grinding table moves relatively, and because the pressure of the grinding head on different areas of the wafer is different, the grinding thickness difference of some areas of the wafer is large, and the grinding thickness difference of other areas of the wafer is small. When the wafer is scanned and detected by the detection equipment, the number of the color difference defects in the area with large thickness difference is often more than that in the area with small thickness difference. Fig. 1 is a schematic distribution diagram of defects on a wafer surface scanned by a related inspection apparatus, and as shown in fig. 1, after the wafer surface is scanned, an image displayed on the wafer surface is divided into four inspection areas, which are an inspection area 201, an inspection area 202, an inspection area 203, and an inspection area 204. Obviously, the number of defects in the inspection area 201, the inspection area 202, and the inspection area 203 is less than the number of defects in the inspection area 204 located at the edge of the wafer, and the black dots in fig. 1 are schematic diagrams of the defects.
At present, when defect detection is performed, a common method is to use a threshold value used for characterizing a defect on a detection area 204 with a serious chromatic aberration defect as a reference threshold value for searching for a defect on a whole wafer. Although the color difference defect can be reduced to the maximum extent, other defects on the wafer, especially residual defects of polycrystalline silicon, are filtered to a great extent, and therefore the accuracy of defect detection is low. Moreover, since the color difference of some areas is too serious, the number of defects reaches the upper scanning limit of the detection device and scanning is terminated, so that the requirement on hardware configuration of the detection device is high, and defect detection is not facilitated.
Disclosure of Invention
The invention aims to provide a wafer defect detection method, which aims to solve the problems that in the prior art, other defects except for chromatic aberration defects are filtered to a great extent, and scanning of detection equipment is stopped due to excessive defect number in certain detection areas.
In order to achieve the above and other objects, the present invention provides a method for detecting wafer defects, comprising:
acquiring an image of the surface of a wafer, and dividing the image of the surface of the wafer into a plurality of detection areas according to the distribution condition of the pressure applied to the surface of the wafer;
selecting a plurality of first detection areas in each detection area, performing differentiation comparison on the first detection areas in each detection area, and obtaining a threshold value used for representing a defect of each detection area according to the result of the differentiation comparison;
dividing each detection area into a plurality of second detection areas, comparing the difference of the second detection areas in each detection area with the threshold value of the corresponding detection area, and if the comparison result meets the preset condition, obtaining the defects existing in the corresponding detection area.
Optionally, a plurality of reference areas are selected in each detection area, each reference area is composed of a plurality of first measurement areas, and centers of the plurality of reference areas are symmetrically distributed with respect to a center of the image of the wafer surface.
Optionally, the differentiation comparison result of the first measurement area in each detection area conforms to a functional relationship between a threshold and the number of defects, and the threshold of each detection area is obtained by querying the functional relationship between the threshold and the number of defects.
Optionally, the number of the reference areas is eight.
Optionally, the threshold is a gray value, and the step of performing differential comparison on the first measurement area in each detection area includes:
the method comprises the following steps: establishing a first plane coordinate system by taking the center of a first measuring area as a first coordinate origin;
step two: taking the center of another first measuring area which is on the same straight line with the center of the first measuring area and is adjacent to the center of the first measuring area as a second coordinate origin, and establishing a second plane coordinate system with the direction consistent with that of the first plane coordinate system;
step three: taking the center of another first measuring area which is on the same straight line with the center of the first measuring area and is adjacent to the center of the first measuring area as a third coordinate origin, and establishing a third plane coordinate system which is consistent with the direction of the first plane coordinate system, wherein the centers of the first measuring area, the another first measuring area and the another first measuring area are connected on the same straight line;
step four: taking a first pixel point in one first measuring region, a second pixel point in the other first measuring region, and a third pixel point in the other first measuring region, wherein the coordinates of the first pixel point, the second pixel point and the third pixel point in the corresponding coordinate systems are the same;
step five: subtracting the gray value of the first pixel point from the gray value of the second pixel point and the gray value of the third pixel point respectively to obtain two difference values;
the number of the first measuring areas in each detecting area is more than three, and steps one to five are executed aiming at any three adjacent first measuring areas with the centers on the same straight line, so that more than two difference values are obtained; to obtain a threshold corresponding to the detection region based on the plurality of differences.
Optionally, the process of obtaining the threshold corresponding to the detection area according to the plurality of difference values includes:
and taking absolute values of the plurality of difference values, wherein the defect number determined by the absolute values of the plurality of difference values accords with the functional relationship between the threshold value and the defect number, so as to obtain the threshold value of the corresponding detection area according to the functional relationship between the threshold value and the defect number.
Optionally, the threshold is a gray value, and the step of performing differential comparison on the second determination region in each detection region includes:
the method comprises the following steps: establishing a first plane coordinate system by taking the center of a second measuring area as a first coordinate origin;
step two: taking the center of another second measuring area which is on the same straight line with the center of the second measuring area and is adjacent to the center of the second measuring area as a second coordinate origin, and establishing a second plane coordinate system with the direction consistent with that of the first plane coordinate system;
step three: taking the center of a second measuring area adjacent to the center of the second measuring area as a third coordinate origin, and establishing a third plane coordinate system with the same direction as the first plane coordinate system, wherein the centers of the second measuring area, the second measuring area and the second measuring area are connected on the same straight line;
step four: taking a first pixel point in one second measurement area, a second pixel point in the other second measurement area, and a third pixel point in the other second measurement area, wherein the coordinates of the first pixel point, the second pixel point and the third pixel point in the corresponding coordinate systems are the same;
step five: subtracting the gray value of the first pixel point from the gray value of the second pixel point and the gray value of the third pixel point respectively to obtain two difference values;
the number of the second measuring areas in each detecting area is more than three, and steps one to five are executed aiming at any three adjacent second measuring areas with centers on the same straight line to obtain more than two difference values;
and then comparing the absolute value of the two difference values obtained by each differentiation comparison with the threshold value of the corresponding scanning area, and if the comparison result meets the preset condition, judging that the corresponding first pixel point is a defect.
Optionally, the preset conditions are:
and the absolute value of each difference value obtained by each differentiation comparison is larger than the threshold value of the corresponding scanning area.
Optionally, after a plurality of first pixel points which are defects are obtained, adjacent first pixel points are combined to obtain the same defect region.
Optionally, the plurality of detection areas at least include:
a circular area located at the center of the wafer surface image; and
a plurality of annular regions concentric with the circular region at the periphery of the circular region.
Compared with the prior art, the method for detecting the wafer defects has the advantages that different defects on the surface of the wafer, particularly color difference defects and polysilicon residual defects, can be captured by setting different thresholds for different detection areas on the surface of the wafer so as to obtain the number of the defects corresponding to the corresponding detection areas, so that the accuracy of defect detection is improved, and the yield of products is also improved by adjusting the production process. Meanwhile, the detection method of the invention sets reasonable threshold values for different detection areas, so that the defect number in each detection area is not too much, the hardware configuration requirement for related detection equipment is reduced, and the related detection equipment cannot reach the scanning upper limit to cause scanning termination due to too much defect number, therefore, the detection method is easy to realize on hardware.
Drawings
FIG. 1 is a schematic view illustrating the distribution of defects on the surface of a wafer scanned by a related inspection apparatus;
FIG. 2 is a flowchart illustrating a method for detecting wafer defects according to an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating a distribution of inspection areas on an image of a wafer surface according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of selecting a reference area on an image of a wafer surface according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a differential alignment of assay regions according to an embodiment of the present invention;
fig. 6 is a schematic diagram illustrating a plurality of defective pixels are merged into a defective area according to an embodiment of the present invention;
FIG. 7 is a graph of threshold as a function of defect number according to an embodiment of the present invention
The reference numerals are explained below:
201/202/203/204-detection area;
301/302/303/304-area where grinding pressure is located;
2041/2042/2043/2044/2045/2046/2047/2048-reference area;
501/502/503-first measurement area/second measurement area;
601/602/603/604-pixel points.
Detailed Description
The following describes in more detail embodiments of the present invention with reference to the schematic drawings. Advantages and features of the present invention will become apparent from the following description and claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
Fig. 2 is a flowchart of a method for detecting a wafer defect according to an embodiment of the present invention, and as shown in fig. 2, the method for detecting a wafer defect includes steps S101, S102, and S103.
Wherein, step S101: the method comprises the steps of obtaining an image of the surface of a wafer, and dividing the image of the surface of the wafer into a plurality of detection areas according to the distribution condition of the pressure applied to the surface of the wafer.
Specifically, in the Poly CMP (polysilicon floating gate chemical mechanical polishing), the polishing head consists of a circular region in the center and a plurality of annular regions concentric with the circular region at the periphery. When the wafer is ground, the grinding head can control different pressures to different areas of the wafer according to the structure of the grinding head, so as to grind the wafer. Due to the different pressures on different areas of the wafer, such a polishing method often results in different flatness in different areas of the wafer. Generally, after a detection device scans the surface of a wafer to obtain an image of the surface of the wafer, the detection device divides different detection areas for the image of the surface of the wafer according to the pressure distribution of the surface area of the wafer.
For example, as shown in fig. 3, the image of the wafer surface of the present embodiment is divided into the following detection areas: a circular pressure distribution area at the center, namely the detection area 201 and the area where the grinding pressure 301 is located; the area next to the detection area 201 is an annular detection area 202, and is also the area where the grinding pressure 302 is located; the area next to the detection area 202 is another annular detection area 203 and is also the area where the grinding pressure 303 is; next, the area next to the detection area 203 is a further annular detection area 204, which is also the area where the grinding pressure 304 is located.
Step S102: selecting a plurality of first measuring areas in each detecting area, carrying out differentiation comparison on the first measuring areas in each detecting area, and obtaining the threshold value of each detecting area according to the result of the differentiation comparison.
Specifically, the threshold is used for characterizing the defect, for example, characterizing the defect by using a gray value of the image, and the threshold is a gray value. The first measurement area is a corresponding detection area, after the detection equipment scans the wafer to obtain an image of the surface of the wafer, a minimum image area, such as a square or rectangular area including a plurality of pixels, is defined on the image of the surface of the wafer, and the size of the minimum image area is determined according to the precision of the detection equipment. More specifically, during the process of detecting the wafer defects in the area, the defects are searched by setting a target value for each detected area, where the target value is the threshold in step 102.
The detection equipment reasonably selects a plurality of reference areas in each detection area, then divides each reference area into areas consisting of a plurality of first measurement areas, then performs differentiation comparison on the first measurement areas, and determines a reasonable threshold value for each detection area according to the comparison result. Preferably, the centers of the plurality of reference areas within each inspection area are symmetrically distributed about the center of the image of the wafer surface. More preferably, the number of reference areas in each detection area is eight.
In this embodiment, the detection device compares the centers of any three adjacent first measurement regions on the same straight line in a differentiation manner. It should be understood that each first measurement region is composed of a plurality of pixel points, and a result after the differential comparison is obtained by selecting one pixel point in the corresponding first measurement region and selecting one pixel point in each of the other two adjacent first measurement regions for the differential comparison (i.e., three pixel points), where the result may be an absolute value of the gray value difference.
Step S103: dividing each detection area into a plurality of second detection areas, performing differentiation comparison on the second detection areas in each detection area, comparing the result of the differentiation comparison with the threshold value of the corresponding detection area, and if the result of the comparison meets the preset condition, obtaining the defects existing on the corresponding detection area.
Specifically, the second measurement area is a corresponding detection area, and after the wafer is scanned by the detection device to obtain the image of the wafer surface, the minimum image area is defined on the image of the wafer surface, that is, the second measurement area includes a plurality of pixels, which may be a square area or a rectangular area. That is, the size of the minimum image area is determined according to the accuracy of the inspection apparatus, and after the image of the wafer surface is obtained, the inspection apparatus divides each inspection area in the image into areas composed of a plurality of second measurement areas, and the second measurement areas are arranged in an array.
Furthermore, the detection device performs differentiation comparison on any three adjacent second measurement areas with the center on the same straight line, and if the result obtained by the differentiation comparison at each time is greater than the threshold set by the corresponding detection area, the detection device determines the pixel point corresponding to the second measurement area as a defect. It should be understood that each second measurement region is composed of a plurality of pixel points, one pixel point is selected in the corresponding second measurement region and is differentiated and compared with one pixel point selected in each of the other two adjacent second measurement regions to obtain a differentiated comparison result, and if the result is greater than a threshold value, the corresponding middle pixel point is determined to be a defect. As in the differential comparison process of the first measurement region, the result of the differential comparison of the second measurement region may be an absolute value of the gray value difference.
In this embodiment, the differentiation comparison result of the first measurement area in each detection area conforms to the functional relationship between the threshold and the number of defects, and the threshold of each detection area is obtained by querying the functional relationship between the threshold and the number of defects. For example, referring to fig. 7, fig. 7 is a graph of threshold value as a function of defect number provided by an embodiment of the present invention, and fig. 7 is obtained by experiments. As shown in fig. 7, the OX axis is the threshold, the OY axis is the defect number, and the curve 701 is a functional relationship curve of the threshold and the residual defect number of the polysilicon; the curve 702 is a functional relationship curve between the threshold and the number of color difference defects, wherein point a is an inflection point on the curve 702, and the threshold selection point is a point corresponding to point a on the X axis.
According to the method for detecting the defects of the wafer, different detection areas are divided for the wafer according to the pressure distribution condition of the chemical mechanical polishing head to different areas of the wafer, and a corresponding threshold value is set for each detection area, so that different defects of each detection area can be captured, and the problem that in the traditional method, the threshold value used for representing the defects at the edge of the wafer is used as the threshold value of the whole detection area, so that the residual defects of polycrystalline silicon in certain areas of the wafer cannot be captured more is solved. Meanwhile, reasonable threshold values are set for different detection areas, so that the defect number of each detection area is not too large, and the requirement on hardware configuration of the detection equipment is reduced.
On the basis of the above-described embodiment, a plurality of reference areas are preferably uniformly distributed in the circumferential direction in each detection area, and ten first measurement areas are selected in each reference area, respectively. The multiple reference areas in each detection area are uniformly distributed along the circumferential direction, so that the obtained threshold value can be closer to the real situation of the corresponding detection area, and the accuracy of defect detection is improved.
In other embodiments, one reference area may be selected in each detection area, but the one reference area is composed of a plurality of first measurement areas.
As shown in fig. 4, eight reference areas are selected from the detection area 201, the detection area 202, the detection area 203, and the detection area 204, respectively. Taking the detection area 204 as an example, eight reference areas are respectively selected, which are the reference area 2041, the reference area 2042, the reference area 2043, the reference area 2044, the reference area 2045, the reference area 2046, the reference area 2047 and the reference area 2048, and each of the reference area 2041, the reference area 2042, the reference area 2043, the reference area 2044, the reference area 2045, the reference area 2046, the reference area 2047 and the reference area 2048 is composed of ten first measurement areas.
Furthermore, in step S102, the step of comparing the differences of the first measurement areas in each detection area specifically includes:
the method comprises the following steps: establishing a first plane coordinate system by taking the center of a first measuring area as a first coordinate origin; such as a rectangular planar coordinate system having a horizontal axis and a vertical axis perpendicular to the horizontal axis;
step two: taking the center of another first measuring area which is on the same straight line with the center of the first measuring area and is adjacent to the center of the first measuring area as a second coordinate origin, and establishing a second plane coordinate system with the direction consistent with that of the first plane coordinate system;
step three: taking the center of a further first measurement region which is on the same straight line with the center of the first measurement region and adjacent to the center of the first measurement region as a third coordinate origin, establishing a third planar coordinate system which is in the same direction as the first planar coordinate system, wherein the centers of the first measurement region, the further first measurement region and the further first measurement region are on the same straight line, and the further first measurement region are located on both sides of the first measurement region;
step four: taking a first pixel point in one first measuring region, a second pixel point in the other first measuring region, and a third pixel point in the other first measuring region, wherein the coordinates of the first pixel point, the second pixel point and the third pixel point in the corresponding coordinate systems are the same;
step five: and subtracting the gray value of the first pixel point from the gray value of the second pixel point and the gray value of the third pixel point respectively to obtain two difference values.
Further, when the number of the first measurement areas in each detection area is more than three, the first measurement areas adjacent to each other and having the centers on the same straight line are subjected to the steps one to five to obtain more than two difference values.
Furthermore, the first origin of coordinates, the second origin of coordinates and the third origin of coordinates may be at the center of the corresponding first measurement area or at some point at the edge of the corresponding first measurement area. In addition, there is no distinction in the execution sequence of the above steps one to three.
For example, as shown in fig. 5, three first measurement regions 501, 502, and 503 in the reference region 2041 are taken, wherein the first measurement region 501 has four vertices A, B, E and F, respectively; the first measurement region 502 further has four vertices B, C, G and F; the first measurement region 503 has four vertices C, D, G and H, respectively. A second planar coordinate system of the first measurement region 501 is established with the point a as the origin of the first measurement region 501, the AB as the X axis, and the AE as the Y axis; similarly, a first planar coordinate system of the first measurement region 502 is established with point B as the origin of the first measurement region 502, BC as the X axis, and BF as the Y axis; similarly, a third plane coordinate system of the first measurement region 503 is established with the point C as the origin of the first measurement region 503, the CD as the X axis, and the CG as the Y axis. Three pixel points A1, B1 and C1 with the same coordinates in three plane coordinate systems are taken. Subtracting the gray value of the point B1 from the gray value of the point A1 to obtain a difference value; this can determine whether pixel point B1 is defective. Similarly, if it is determined whether the pixel point a1 is defective, the above operations may be performed on different pixel points in the first measurement area 502, so as to obtain two other differences. In turn, each of the first measurement areas in the reference area 2041 is subjected to the above operations, and a plurality of differences can be obtained. Similarly, by performing the above operation on each of the first measurement areas 2041 to 2048, a large difference can be obtained.
Since the absolute values of these differences are, in one embodiment, a function of the threshold and the number of defects, the threshold and the number of defects can be looked up to obtain the threshold of the reference area 2041,
in step S103, the step of performing a differential alignment on the second measurement region in each detection region includes:
the method comprises the following steps: establishing a first plane coordinate system by taking the center of a second measuring area as a first coordinate origin;
step two: taking the center of another second measuring area which is on the same straight line with the center of the second measuring area and is adjacent to the center of the second measuring area as a second coordinate origin, and establishing a second plane coordinate system with the direction consistent with that of the first plane coordinate system;
step three: taking the center of a second measurement region adjacent to the center of the second measurement region as a third coordinate origin, and establishing a third planar coordinate system with the same direction as the first planar coordinate system, wherein the centers of the second measurement region, the second measurement region and the second measurement region are connected on the same straight line, and the second measurement region are located on both sides of the second measurement region;
step four: taking a first pixel point in one second measurement area, a second pixel point in the other second measurement area, and a third pixel point in the other second measurement area, wherein the coordinates of the first pixel point, the second pixel point and the third pixel point in the corresponding coordinate systems are the same;
step five: and subtracting the gray value of the first pixel point from the gray value of the second pixel point and the gray value of the third pixel point respectively to obtain two difference values.
And when the number of the second measuring areas in each detecting area is more than three, executing the first step to the fifth step aiming at any three adjacent second measuring areas with centers on the same straight line so as to obtain more than two difference values. Similarly, step one to step three herein are not performed sequentially.
The differential alignment herein refers to the implementation process of the differential alignment of the first determination region, which is not described herein.
After more than two differences are obtained, the process of obtaining corresponding defects is as follows: and taking respective absolute values of two difference values obtained by each differentiation comparison, and if the absolute values of the two difference values are greater than the threshold value of the corresponding detection area, judging that the first pixel point subjected to differentiation comparison is a defect. The first pixel point is the middle pixel point in each differentiation comparison process.
For example, as shown in fig. 5, it is assumed that the threshold value of one of the detection regions is 20. The gray value of the middle pixel point B1 is 80, the gray value of the left pixel point a1 adjacent to the middle pixel point is 50, and the gray value of the right pixel point C1 adjacent to the middle pixel point is 120. The absolute value of the difference between the gray value of the a1 pixel and the gray value of the B1 pixel is 30, the absolute value of the difference between the gray value of the a1 pixel and the gray value of the C1 pixel is 40, and both the absolute values 30 and 40 of the two differences are greater than the threshold 20 of the detection area, so that the middle pixel B1 can be determined to be a defect.
Further, as shown in fig. 6, if the pixel 601, the pixel 602, the pixel 603, and the pixel 604 are all determined as defective pixels through differentiation and comparison, and the defective pixel 601, the defective pixel 602, the defective pixel 603, and the defective pixel 604 are adjacent to each other in the manner shown in fig. 6, the defective pixel 601, the defective pixel 602, the defective pixel 603, and the defective pixel 604 are merged into the same defect. Thus, the area of the defect area is large enough to be observed by human eyes.
In the preferred embodiment of the present invention, for example, when the detection area is divided according to the pressure distribution on the wafer surface, the middle of the detection area is a circular area, and the outer side of the central area is also a triangular area or a square area. In addition, the number of detection regions is not limited to four. The shape of the first measurement region and the second measurement region is not limited to a rectangle or a square.
In summary, the wafer defect detection method provided by the invention sets different thresholds for different detection areas of the image on the wafer surface, so as to obtain the number of defects corresponding to the corresponding detection areas, and thus, different defects on the wafer surface, especially color difference defects and polysilicon residual defects can be captured, thereby improving the accuracy of defect detection, and improving the product yield by adjusting the production process. Meanwhile, the detection method of the invention sets reasonable threshold values for different detection areas, so that the defect number in each detection area is not excessive, the hardware configuration requirement for related detection equipment is reduced, and the detection equipment cannot cause scanning termination because the defect number reaches the upper scanning limit excessively, therefore, the detection method is easy to realize on hardware.
The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. A method for detecting wafer defects is characterized by comprising the following steps:
acquiring an image of the surface of a wafer, and dividing the image of the surface of the wafer into a plurality of detection areas according to the distribution condition of the pressure applied to the surface of the wafer;
selecting a plurality of first detection areas in each detection area, performing differentiation comparison on the first detection areas in each detection area, and obtaining a threshold value used for representing a defect of each detection area according to the result of the differentiation comparison;
dividing each detection area into a plurality of second detection areas, comparing the result of the difference comparison with the threshold value of the corresponding detection area after the difference comparison of the second detection areas in each detection area, and if the result of the comparison meets the preset condition, obtaining the defects existing on the corresponding detection area;
the threshold is a gray value, and the process of performing differential comparison on the first determination area in each detection area comprises the following steps:
the method comprises the following steps: establishing a first plane coordinate system by taking the center of a first measuring area as a first coordinate origin;
step two: taking the center of another first measuring area which is on the same straight line with the center of the first measuring area and is adjacent to the center of the first measuring area as a second coordinate origin, and establishing a second plane coordinate system with the direction consistent with that of the first plane coordinate system;
step three: taking the center of another first measuring area which is on the same straight line with the center of the first measuring area and is adjacent to the center of the first measuring area as a third coordinate origin, and establishing a third plane coordinate system which is consistent with the direction of the first plane coordinate system, wherein the centers of the first measuring area, the another first measuring area and the another first measuring area are connected on the same straight line;
step four: taking a first pixel point in one first measuring region, a second pixel point in the other first measuring region, and a third pixel point in the other first measuring region, wherein the coordinates of the first pixel point, the second pixel point and the third pixel point in the corresponding coordinate systems are the same;
step five: subtracting the gray value of the first pixel point from the gray value of the second pixel point and the gray value of the third pixel point respectively to obtain two difference values;
the number of the first measuring areas in each detecting area is more than three, and steps one to five are executed aiming at any three adjacent first measuring areas with the centers on the same straight line, so that more than two difference values are obtained; so as to obtain the threshold value of the corresponding detection area according to the plurality of difference values.
2. The method as claimed in claim 1, wherein a plurality of reference areas are selected in each of the inspection areas, each of the reference areas is composed of a plurality of first measurement areas, and centers of the plurality of reference areas are symmetrically distributed with respect to a center of the image of the wafer surface.
3. The method as claimed in claim 2, wherein the difference comparison result of the first measurement area in each of the measurement areas is in accordance with a functional relationship between a threshold and a defect number, and the threshold of each of the measurement areas is obtained by querying the functional relationship between the threshold and the defect number.
4. The method as claimed in claim 2, wherein the number of the reference regions is eight.
5. The method as claimed in claim 1, wherein the step of obtaining the threshold corresponding to the detected area according to the plurality of differences comprises:
and taking absolute values of the plurality of difference values, wherein the defect number determined by the absolute values of the plurality of difference values accords with the functional relationship between the threshold value and the defect number, so as to obtain the threshold value of the corresponding detection area according to the functional relationship between the threshold value and the defect number.
6. The method according to claim 1, wherein the threshold is a gray value, and the step of comparing the differences of the second measurement areas in each of the detection areas comprises:
the method comprises the following steps: establishing a first plane coordinate system by taking the center of a second measuring area as a first coordinate origin;
step two: taking the center of another second measuring area which is on the same straight line with the center of the second measuring area and is adjacent to the center of the second measuring area as a second coordinate origin, and establishing a second plane coordinate system with the direction consistent with that of the first plane coordinate system;
step three: taking the center of a second measuring area adjacent to the center of the second measuring area as a third coordinate origin, and establishing a third plane coordinate system with the same direction as the first plane coordinate system, wherein the centers of the second measuring area, the second measuring area and the second measuring area are connected on the same straight line;
step four: taking a first pixel point in one second measurement area, a second pixel point in the other second measurement area, and a third pixel point in the other second measurement area, wherein the coordinates of the first pixel point, the second pixel point and the third pixel point in the corresponding coordinate systems are the same;
step five: subtracting the gray value of the first pixel point from the gray value of the second pixel point and the gray value of the third pixel point respectively to obtain two difference values;
the number of the second measuring areas in each detecting area is more than three, and steps one to five are executed aiming at any three adjacent second measuring areas with centers on the same straight line to obtain more than two difference values;
and then comparing the absolute value of the two difference values obtained by each differentiation comparison with the threshold value of the corresponding scanning area, and if the comparison result meets the preset condition, judging that the corresponding first pixel point is a defect.
7. The method for detecting wafer defects as claimed in claim 6, wherein the predetermined conditions are:
and the absolute value of each difference value obtained by each differentiation comparison is larger than the threshold value of the corresponding scanning area.
8. The wafer defect detection method of claim 7, wherein after obtaining a plurality of first pixels that are defects, adjacent first pixels are merged to obtain a same defect region.
9. The method of claim 1, wherein the plurality of inspection areas at least comprise:
a circular area located at the center of the wafer surface image; and
a plurality of annular regions concentric with the circular region at the periphery of the circular region.
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| CN107910276A (en) * | 2017-11-24 | 2018-04-13 | 上海华力微电子有限公司 | A kind of wafer defect detection method |
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| CN111855663B (en) * | 2019-04-30 | 2023-06-27 | 芯恩（青岛）集成电路有限公司 | Equipment and method for detecting wafer defects |
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| CN117046735B (en) * | 2023-10-12 | 2023-12-12 | 江苏芯德半导体科技有限公司 | Method and system for merging and distributing patterns of multiple chips in wafer |
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