OVERLAY MEASUREMENT USING SCATTEROMETRY IDENTIFICATION METHOD

摘要

PROBLEM TO BE SOLVED: To provide a method for determining non-destructive characteristics for an aligning overlay between two layers of a semiconductor wafer.

SOLUTION: In one embodiment as a function of wavelengths and incident angles, radiation of an incident beam is directed onto the surface of a wafer to determine characteristics of a diffraction beam thus obtained. The diffraction beam decomposed into a spectrum and an angle is associated with an alignment for overlay features. A library of a calculated diffraction spectrum is established by modeling an entire range of expected variations in the overlay alignment. A spectrum obtained by an inspection for an actual wafer possessing in at least two layers having an alignment target is compared with the library so as to identify a best fit in order to determine an actual alignment characteristics. A result of the comparison is employed as an input/or inputs to upstream/downstream processing control.

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