Defects are detected using surface topography data. The defects may be detected by determining topography characteristics within a region of interest on a sample, and the same topography characteristics of at least one reference surface. By comparing the topography characteristics in the region of i
Defects are detected using surface topography data. The defects may be detected by determining topography characteristics within a region of interest on a sample, and the same topography characteristics of at least one reference surface. By comparing the topography characteristics in the region of interest for the sample and reference surface, common pattern structures may be removed, leaving only variations, which may be used to identify the presence of defects. For example, thresholds may be used to identify variations in the topography characteristics as defect candidates. Defects may be identified based on, e.g., size, height, shape, texture, etc. of candidate defects. In some implementations, rather than using a reference surface, the topography characteristic of the surface within the region of interest may be inspected based on prior knowledge of a required surface topography for the region of interest to determine if a defect is present.
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1. An optical inspection apparatus configured to detect a defect in a test region of interest on a sample, the optical inspection apparatus comprising: a light source that produces an illumination beam of light that is incident on the sample and reflected by the sample;at least one detector array th
1. An optical inspection apparatus configured to detect a defect in a test region of interest on a sample, the optical inspection apparatus comprising: a light source that produces an illumination beam of light that is incident on the sample and reflected by the sample;at least one detector array that receives the light after it is reflected by the sample to obtain optical data from the sample, the optical data comprising a plurality of pixels;at least one processor coupled to the at least one detector array to receive the optical data, wherein the at least one processor is configured to: determine a test topography characteristic for each pixel in the test region of interest of the sample from the optical data; andcompare the test topography characteristic for each pixel to a reference topography characteristic for each corresponding pixel in a region of interest of at least one reference surface, the region of interest of the at least one reference surface having a same by design pattern as the test region of interest on the sample to determine a presence of the defect in the test region of interest on the sample. 2. The optical inspection apparatus of claim 1, wherein the optical inspection apparatus is an interferometer and the optical data comprises interferometer data. 3. The optical inspection apparatus of claim 2, wherein the at least one detector array comprises a single detector array with a plurality of pixels, the optical inspection apparatus further comprising a phase shift mask comprising an array of phase shift pixels aligned with the plurality of pixels of the single detector array, wherein the interferometer data comprises an image of the test region of interest, wherein the image comprises a plurality of phase shift measurements for the test region of interest. 4. The optical inspection apparatus of claim 2, wherein the at least one detector array comprises a plurality of detector arrays each with a plurality of pixels, the optical inspection apparatus further comprising a corresponding plurality of polarizers with each with a different orientation before each detector array to produce a different phase shift measurement, wherein the interferometer data comprises a plurality of images of the test region of interest that are simultaneously captured, wherein each of the plurality of images comprises different phase shift measurements for the test region of interest. 5. The optical inspection apparatus of claim 1, wherein the at least one processor is configured to determine the test topography characteristic for each pixel by being configured to determine a surface height value for each pixel in the test region of interest. 6. The optical inspection apparatus of claim 1, wherein the at least one processor is configured to determine the test topography characteristic for each pixel using neighboring pixels surrounding each pixel. 7. The optical inspection apparatus of claim 6, wherein the at least one processor is configured to determine the test topography characteristic each pixel by being configured to determine a statistical property for each pixel based on surface height values for the neighboring pixels surrounding each pixel. 8. The optical inspection apparatus of claim 7, wherein the statistical property comprises a standard deviation. 9. The optical inspection apparatus of claim 1, wherein the at least one processor is configured to compare the test topography characteristics for each pixel to the reference topography characteristic for each corresponding pixel in the region of interest of the at least one reference surface to determine the presence of the defect by being configured to: generate a topography characteristics difference for each pixel in the test region of interest of the sample;identify pixels with the topography characteristics difference exceeding a predetermined threshold; andidentify the presence of the defect using the pixels with the topography characteristics difference exceeding the predetermined threshold. 10. The optical inspection apparatus of claim 1, wherein the at least one processor is configured to compare the test topography characteristics for each pixel to the reference topography characteristic for each corresponding pixel in the region of interest of the at least one reference surface to determine the presence of the defect by being configured to: group pixels together based on the comparison of the test topography characteristics for each pixel to the reference topography characteristic for each corresponding pixel into one or more candidate defects;generate one or more descriptors for the one or more candidate defects, wherein the one or more descriptors comprise at least one of lateral size, height, shape, roughness, and texture; andfilter the one or more candidate defects using the one or more descriptors to identify a candidate defect as the defect. 11. The optical inspection apparatus of claim 10, wherein the at least one processor is configured to filter the one or more candidate defects using the one or more descriptors to identify the candidate defect as the defect by being configured to filter using one or more of lateral size, height, shape, roughness, texture, or a combination thereof. 12. The optical inspection apparatus of claim 1, wherein the at least one reference surface comprises a plurality of different types of reference surfaces. 13. The optical inspection apparatus of claim 12, wherein the plurality of different types of reference surfaces comprises two or more of a local reference surface, a non- local reference surface, and a golden reference surface, wherein the local reference surface comprises a surface from at least one local region of interest on the sample, the non-local reference surface comprises a surface from at least one non-local region of interest on the sample, and the golden reference surface comprises a surface from at least one region of interest on one or more different samples. 14. The optical inspection apparatus of claim 13, wherein the sample is a semiconductor wafer comprising a plurality of dies, and wherein the at least one local region of interest on the sample comprises at least one region of interest on the semiconductor wafer that is no more than one die away from the test region of interest of the sample, the at least one non-local region of interest on the sample comprises at least one region of interest on the semiconductor wafer that is more than one die away from the test region of interest of the sample. 15. The optical inspection apparatus of claim 1, wherein the at least one reference surface comprises a reference surface generated as a statistical combination of a plurality of reference surfaces. 16. The optical inspection apparatus of claim 1, wherein the defect in the test region of interest on the sample is one of residue, dishing, edge roll-off, hotspot, pit, scratch, and bridge. 17. The optical inspection apparatus of claim 1, wherein the at least one processor is configured to transmit defect data including the presence of the defect in the test region of interest on the sample. 18. An optical inspection apparatus configured to detect a defect, the optical inspection apparatus comprising: a light source that produces an illumination beam of light that is incident on a sample and reflected by the sample;at least one detector array that receives the light after it is reflected by the sample to obtain optical data from the sample, the optical data comprising a plurality of pixels;at least one processor coupled to the at least one detector array to receive the optical data, wherein the at least one processor is configured to: determine a topography characteristic for each pixel in a region of interest of the sample from the optical data; anddetermine a presence of the defect in the region of interest using the topography characteristic for each pixel in the region of interest and prior knowledge of a required topography characteristic for the region of interest. 19. The optical inspection apparatus of claim 18, wherein the optical inspection apparatus is an interferometer and the optical data comprises interferometer data. 20. The optical inspection apparatus of claim 19, wherein the at least one detector array comprises a single detector array with a plurality of pixels, the optical inspection apparatus further comprising a phase shift mask comprising an array of phase shift pixels aligned with the plurality of pixels of the single detector array, wherein the interferometer data comprises an image of the region of interest, wherein the image comprises a plurality of phase shift measurements for test region of interest. 21. The optical inspection apparatus of claim 19, wherein the at least one detector array comprises a plurality of detector arrays each with a plurality of pixels, the optical inspection apparatus further comprising a corresponding plurality of polarizers with each with a different orientation before each detector array to produce a different phase shift measurement, wherein the interferometer data comprises a plurality of images of the region of interest that are simultaneously captured, wherein each of the plurality of images comprises different phase shift measurements for the region of interest. 22. The optical inspection apparatus of claim 18, wherein the region of interest is an overlay target. 23. The optical inspection apparatus of claim 22, wherein the defect is an asymmetry in the topography characteristic of the overlay target. 24. The optical inspection apparatus of claim 18, wherein the at least one processor is configured to transmit defect data including the presence of the defect in the region of interest on the sample. 25. An optical inspection apparatus configured to detect a defect in a test region of interest on a sample, the optical inspection apparatus comprising: a light source that produces an illumination beam of light that is incident on the sample and reflected by the sample;at least one detector array that receives the light after it is reflected by the sample to obtain optical data from the sample, the optical data comprising a plurality of pixels;means for determining a test topography characteristic for each pixel in the test region of interest of the sample from the optical data; andmeans for comparing the test topography characteristic for each pixel to a reference topography characteristic for each corresponding pixel in a region of interest of at least one reference surface, the region of interest of the at least one reference surface having a same by design pattern as the test region of interest on the sample to determine a presence of the defect in the test region of interest on the sample. 26. The optical inspection apparatus of claim 25, wherein the optical inspection apparatus is an interferometer and the optical data comprises interferometer data. 27. The optical inspection apparatus of claim 26, wherein the at least one detector array comprises a single detector array with a plurality of pixels, the optical inspection apparatus further comprising a phase shift mask comprising an array of phase shift pixels aligned with the plurality of pixels of the single detector array, wherein the interferometer data comprises an image of the test region of interest, wherein the image comprises a plurality of phase shift measurements for the test region of interest. 28. The optical inspection apparatus of claim 26, wherein the at least one detector array comprises a plurality of detector arrays each with a plurality of pixels, the optical inspection apparatus further comprising a corresponding plurality of polarizers with each with a different orientation before each detector array to produce a different phase shift measurement, wherein the interferometer data comprises a plurality of images of the test region of interest that are simultaneously captured, wherein each of the plurality of images comprises different phase shift measurements for the test region of interest. 29. The optical inspection apparatus of claim 25, wherein the test topography characteristic for each pixel in the test region of interest comprises a surface height value for each pixel in the test region of interest. 30. The optical inspection apparatus of claim 25, wherein the test topography characteristic for each pixel in the test region of interest is determined using neighboring pixels surrounding each pixel. 31. The optical inspection apparatus of claim 30, wherein the test topography characteristic each pixel comprises a statistical property of surface height values for the neighboring pixels surrounding each pixel. 32. The optical inspection apparatus of claim 31, wherein the statistical property comprises a standard deviation. 33. The optical inspection apparatus of claim 25, wherein the means for comparing comprises: means for generating a topography characteristics difference for each pixel in the test region of interest of the sample;means for identifying pixels with the topography characteristics difference exceeding a predetermined threshold; andmeans for identifying the presence of the defect using the pixels with the topography characteristics difference exceeding the predetermined threshold. 34. The optical inspection apparatus of claim 25, wherein the means for comparing comprises: means for grouping pixels together based on the comparison of the test topography characteristics for each pixel to the reference topography characteristic for each corresponding pixel into one or more candidate defects;means for generating one or more descriptors for the one or more candidate defects, wherein the one or more descriptors comprise at least one of lateral size, height, shape, roughness, and texture; andmeans for filtering the one or more candidate defects using the one or more descriptors to identify a candidate defect as the defect. 35. The optical inspection apparatus of claim 34, wherein the means for filtering the one or more candidate defects using the one or more descriptors to identify the candidate defect as the defect filters uses one or more of lateral size, height, shape, roughness, texture, or a combination thereof. 36. The optical inspection apparatus of claim 25, wherein the at least one reference surface comprises a plurality of different types of reference surfaces. 37. The optical inspection apparatus of claim 36, wherein the plurality of different types of reference surfaces comprises two or more of a local reference surface, a non-local reference surface, and a golden reference surface, wherein the local reference surface comprises a surface from at least one local region of interest on the sample, the non-local reference surface comprises a surface from at least one non-local region of interest on the sample, and the golden reference surface comprises a surface from at least one region of interest on one or more different samples. 38. The optical inspection apparatus of claim 37, wherein the sample is a semiconductor wafer comprising a plurality of dies, and wherein the at least one local region of interest on the sample comprises at least one region of interest on the semiconductor wafer that is no more than one die away from the test region of interest of the sample, the at least one non-local region of interest on the sample comprises at least one region of interest on the semiconductor wafer that is more than one die away from the test region of interest of the sample. 39. The optical inspection apparatus of claim 25, wherein the at least one reference surface comprises a reference surface generated as a statistical combination of a plurality of reference surfaces. 40. The optical inspection apparatus of claim 25, wherein the defect in the test region of interest on the sample is one of residue, dishing, edge roll-off, hotspot, pit, scratch, and bridge. 41. The optical inspection apparatus of claim 25, further comprising means for transmitting defect data including the presence of the defect in the test region of interest on the sample.
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