Broadband light interferometry for focal-map generation in photomask inspection
AssigneeKLA Corporation
InventorsRui-Fang Shi, Dmitry Skvortsov
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Abstract
Heights on a surface of a photomask are measured using broadband light interferometry. The heights include heights of patterned areas of the photomask. A focal map is produced from the measured heights on the surface of the photomask. To produce the focal map, the measured heights of the patterned areas are adjusted based on fill factors for the patterned areas. The photomask is inspected for defects, using the focal map.
Claims22
A method, comprising:
- measuring heights on a surface of a photomask using broadband light interferometry, the heights comprising heights of patterned areas of the photomask;
- producing a focal map from the measured heights on the surface of the photomask, comprising adjusting the measured heights of the patterned areas based on fill factors for the patterned areas;
- and
- inspecting the photomask for defects, using the focal map.
A photomask-inspection system, comprising:
- a broadband light interferometer;
- photomask-inspection optics;
- one or more processors;
- and
- memory storing one or more programs for execution by the one or more processors, the one or more programs comprising instructions for:
- measuring heights on a surface of a photomask using the broadband light interferometer, the heights comprising heights of patterned areas of the photomask;
- producing a focal map from the measured heights on the surface of the photomask, comprising adjusting the measured heights of the patterned areas based on fill factors for the patterned areas;
- and
- inspecting the photomask for defects with the photomask-inspection optics, using the focal map.
A non-transitory computer-readable storage medium storing one or more programs for execution by one or more processors of a photomask-inspection system that further comprises a broadband light interferometer and photomask-inspection optics, the one or more programs including instructions for:
- measuring heights on a surface of a photomask using broadband light interferometry, the heights comprising heights of patterned areas of the photomask;
- producing a focal map from the measured heights on the surface of the photomask, comprising adjusting the measured heights of the patterned areas based on fill factors for the patterned areas;
- and
- inspecting the photomask for defects with the photomask-inspection optics, using the focal map.
Dependencies are inferred from the claim text.