Thin-film thickness profile and its refractive index measurements by dispersive white-light interferometry.

As an extension of the authors' previous report of Ref 1, we describe an improved version of dispersive white-light interferometry that enables us to measure the tomographical thickness profile of a thin-film layer through Fourier-transform analysis of spectrally-resolved interference signals. The group refractive index can also be determined without prior knowledge of the geometrical thickness of the film layer. Owing to fast measurement speed with no need of mechanical depth scanning, the proposed method is well suited for in-line 3-D inspection of dielectric thin film layers particularly for the semiconductor and flat-panel display industry.