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Spectroscopic Ellipsometric Analysis of a Si Grating Pattern Made by Photolithography

We performed spectroscopic ellipsometry (SE) measurements to investigate the possibility of a nondestructive in-situ monitoring tool for determining the critical dimension (CD) of patterned structures. A simple 1D patterned c-Si periodic structure was measured from the zeroth-order diffraction response at a fixed angle of incidence, whose result agreed with the theoretical prediction made by using a rigorous coupled-wave analysis (RCWA) calculation for the reflected light. To investigate the SE’s advantage over atomic force microscopy we also prepared a c-Si periodic structure with a Cr hat on the top. We observed that the theoretical result could also explain the measured spectra quantitatively even when the metallic hat structure on the top acted as a strong obstacle to the probing light.