Coating film and asymmetric amplitude difference effects on measurement performance in phase grating interference-based metrology.

ABSTRACT

In this study, the effects of the coating film thickness on a grating interferometry system were analyzed. The asymmetry-induced error of the deformed phase grating varied periodically with the coating film thickness, due to the spurious interference of multiple reflections in the film layer and asymmetry in the amplitudes of the diffraction orders, which led to phase offsets (and thus position errors). The average error obtained with a multiorder interferometer was compared to that simulated by atomic force microscopy. The simulation and measurement results were consistent with the theoretical analysis, which will facilitate accurate measurement error analysis.