Segmentation for wafer inspection
Methods and systems for segmenting pixels for wafer inspection are provided. One method includes determining a statistic for individual pixels based on a characteristic of the individual pixels in an image acquired for a wafer by an inspection system. The method also includes assigning the individual pixels to first segments based on the statistic. In addition, the method includes detecting one or more edges between the first segments in an image of the first segments and generating an edge map by projecting the one or more edges across an area corresponding to the image for the wafer. The method further includes assigning the individual pixels to second segments by applying the first segments and the edge map to the image for the wafer thereby segmenting the image. Defect detection is performed based on the second segments to which the individual pixels are assigned.
1. A computer-implemented method for segmenting pixels in an image of a wafer for defect detection, comprising:
determining a statistic for individual pixels based on a characteristic of the individual pixels in an image acquired for a wafer by an inspection system;
assigning the individual pixels to first segments based on the statistic;
detecting one or more edges between the first segments in an image of the first segments;
generating an edge map by projecting the one or more edges across an area corresponding to the image for the wafer; and
assigning the individual pixels to second segments by applying the first segments and the edge map to the image for the wafer thereby segmenting the image, wherein defect detection is performed based on the second segments to which the individual pixels are assigned, and wherein steps of the method are performed by a computer system.
2. The method of claim 1 , wherein the characteristic is image intensity of the individual pixels.
3. The method of claim 1 , wherein the statistic is median image intensity of the individual pixels.
4. The method of claim 1 , further comprising generating an image showing the statistic determined for the individual pixels, wherein assigning the individual pixels to the first segments is performed based on the image showing the statistic.
5. The method of claim 1 , further comprising generating the image of the first segments by labeling the individual pixels based on the first segments to which the individual pixels were assigned.
6. The method of claim 1 , wherein the one or more edges comprise at least one edge that extends in the x direction, at least one edge that extends in the y direction, or a combination of at least one edge that extends in the x direction and at least one edge that extends in the y direction.
7. The method of claim 1 , further comprising modifying the one or more detected edges before said generating based on spatial characteristics of the one or more detected edges.
8. The method of claim 1 , wherein assigning the individual pixels to the second segments comprises generating the second segments based on the first segments and the edge map and applying the second segments to the individual pixels.
9. The method of claim 1 , wherein assigning the individual pixels to the first segments results in the individual pixels having different levels of noise assigned to different first segments.
10. The method of claim 1 , wherein at least one of the first segments corresponds to a region on the wafer containing structures having a first characteristic, and wherein at least another of the first segments corresponds to a region on the wafer containing structures having a second characteristic that is different than the first characteristic.
11. The method of claim 1 , wherein at least one of the second segments corresponds to a region on the wafer containing structures having a first characteristic, and wherein at least another of the second segments corresponds to a region on the wafer containing structures having a second characteristic that is different than the first characteristic.
12. The method of claim 1 , wherein at least one of the first segments corresponds to a page break region of a device being fabricated on the wafer, and wherein at least another of the first segments corresponds to an array region of the device.
13. The method of claim 1 , wherein at least one of the second segments corresponds to a page break region of a device being fabricated on the wafer, and wherein at least another of the second segments corresponds to an array region of the device.
14. The method of claim 1 , wherein the method is performed during scanning of the wafer by the inspection system.
15. The method of claim 1 , wherein the image for the wafer comprises one of multiple image frames acquired sequentially for different areas on the wafer during scanning of the wafer by the inspection system.
16. The method of claim 1 , wherein the image for the wafer comprises one of multiple image frames acquired sequentially for different areas on the wafer during scanning of the wafer by the inspection system, and wherein the method is performed for more than one of the multiple image frames.
17. The method of claim 1 , wherein the image for the wafer comprises one of multiple image frames acquired simultaneously for one area on the wafer by multiple detection subsystems of the inspection system, and wherein the method further comprises assigning individual pixels in at least one other of the multiple image frames to the second segments by applying the first segments and the edge map to the at least one other of the multiple image frames.
18. The method of claim 1 , wherein the inspection system is a dark field inspection system.
19. A non-transitory computer-readable medium storing program instructions executable on a computer system for performing a method for segmenting pixels in an image of a wafer for defect detection, wherein the method comprises:
determining a statistic for individual pixels based on a characteristic of the individual pixels in an image acquired for a wafer by an inspection system;
assigning the individual pixels to first segments based on the statistic;
detecting one or more edges between the first segments in an image of the first segments;
generating an edge map by projecting the one or more edges across an area corresponding to the image for the wafer; and
assigning the individual pixels to second segments by applying the first segments and the edge map to the image for the wafer thereby segmenting the image, wherein defect detection is performed based on the second segments to which the individual pixels are assigned.
20. A system configured to segment pixels in an image of a wafer for defect detection, comprising:
an inspection subsystem configured to generate an image for a wafer; and
a computer subsystem configured for:
determining a statistic for individual pixels based on a characteristic of the individual pixels in the image for the wafer;
assigning the individual pixels to first segments based on the statistic;
detecting one or more edges between the first segments in an image of the first segments;
generating an edge map by projecting the one or more edges across an area corresponding to the image for the wafer; and
assigning the individual pixels to second segments by applying the first segments and the edge map to the image for the wafer thereby segmenting the image, wherein defect detection is performed based on the second segments to which the individual pixels are assigned.