Method and apparatus for high-throughput inspection of large flat patterned media using dynamically programmable optical spatial filtering

摘要

In an inspection system for planar objects having periodic structures, programmable optical Fourier filtering in the focal plane of a telecentric lens system is used to directly identify physical phenomena indicative of non-periodic defects. Lens assemblies and a coherent optical source are used to generate and observe a spatial Fourier transform of a periodic structure in the Fourier plane. Optical Fourier filtering (OFF) is performed in the focal plane using an electrically programmable and electrically alignable spatial light modulator. The spatial light modulator with high signal to noise ratio is electrically reconfigurable according to a feedback-driven, filter construction and alignment algorithm. The OFF enhances any non-periodic components present in the Fourier plane and final image plane of the object. A system having a plurality of inspection channels provides high-throughput inspection of objects with small non-periodic defects while maintaining high detection sensitivity.