Advanced cell-to-cell inspection
View Patent ↗Inspection of objects such as semiconductor wafers may proceed on a cell-to-cell or die-to-die basis. An image of a wafer may be obtained and the cells or dies shown therein can be inspected using any combination of appropriate die-to-die or cell-to-cell inspection methods. For example, one or more areas may be designated for cell-to-cell inspection. For each cell type, a reference image can be generated by obtaining an image of the area and displacing the image by an amount equal to the repetition vector for that cell type in opposite directions. The displaced images and the original image can be combined into a single reference image. The original image can then be compared to the reference image. In some embodiments, the displaced images are also compared to the reference image to statistically determine the presence or absence of defects.
1. An electro-optical inspection method comprising:
imaging at least a portion of a semiconductor wafer, wherein (i) the wafer includes at least two regions, including a first region comprising a plurality of memory cells of a first type and a second region comprising a plurality of memory cells of a second type, and (ii) a repetition vector of at least one type of cells is different from a repetition vector of at least one other type of cells;
accessing data that defines at least one repetition vector for each type of cells; and
inspecting each region using a cell-to-cell comparison method based on data including the at least one repetition vector for the type of cells in each respective region.
2. The method as set forth in claim 1 , wherein the inspecting includes, for at least one of the first and second regions:
generating at least one displaced image of the at least one region, including displacing an image of the at least one region by an integer multiple of the at least one repetition vector for the type of cells in the at least one region.
3. The method as set forth in claim 2 , wherein the inspecting further includes, for at least one of the first and second regions:
comparing the at least one displaced image to a reference image of the at least one region; and
based on the comparison, identifying whether any defects or defect candidates have been detected in the at least one region.
4. The method asset forth in claim 2 , wherein a plurality of displaced images are generated.
5. The method as set forth in claim 2 , further comprising:
generating a reference image based on data including an image of the at least one region and the at least one displaced image.
6. The method as set forth in claim 1 , wherein the repetition vectors differ in repetition size.
7. The method as set forth in claim 1 , wherein the repetition vectors differ in repetition direction.
8. The method as set forth in claim 1 , wherein the repetition vectors differ in both repetition direction and repetition size.
9. The method as set forth in claim 1 , wherein the imaging includes generating a single image including the at least two regions.
10. The method as set forth in claim 1 , wherein each of the at least two regions is inspected by a single processor in sequence.
11. The method as set forth in claim 1 , further comprising generating a reference image for each type of memory cell.
12. An electro-optical inspection method comprising:
imaging at least one portion of a semiconductor wafer along an inspection path, wherein the wafer includes at least one region comprising a plurality of memory cells having a repetition vector that is perpendicular to the inspection path and is an only repetition vector associated with the at least one region; and
inspecting the at least one portion of the semiconductor wafer using a cell-to-cell comparison method.
13. An electro-optical inspection system, the system comprising:
a light source configured to illuminate a wafer,
an imager configured to image the wafer; and
at least one processing unit configured to perform actions including: (i) obtaining an inspection image of at least a portion of the wafer including at least two regions, each region having a repetition vector different from one another, (ii) accessing data that defines the repetition vector for each region, and (iii) inspecting each region using a cell-to-cell comparison method based on the repetition vector of each region.
14. The system as set forth in claim 13 , wherein the repetition vectors differ in repetition size.
15. The system as set forth in claim 13 , wherein the repetition vectors differ in repetition direction.
16. The system as set forth in claim 13 , wherein the repetition vectors differ in repetition size and repetition direction.
17. The system as set forth in claim 13 , wherein the processing unit is configured to obtain a single image including the at least two regions.
18. The system as set forth in claim 17 , wherein the processing unit is further configured to inspect each of the at least two regions in sequence.
19. An electro-optical inspection system, the system comprising:
a light source configured to illuminate a wafer;
an imager configured to image the wafer along an inspection path; and
at least one processing unit; configured to perform actions including:
(i) obtaining an inspection image of at least a portion of the wafer including a region defined by structural features having a repetition vector that is perpendicular to the inspection path and is an only repetition vector associated with the region, (ii) accessing data that defines the repetition vector, and (iii) inspecting the region using a cell-to-cell comparison method based on the repetition vector.