Snapshot thickness profile cross-sectioning for a warped substrate with non-uniform sub-100 nm ultra-thin film

This paper describes dynamic spectro-ellipsometric interferometry (DSEI), which simultaneously measures ultra-thin film thickness and surface profile non-destructively. The proposed snapshot-scheme DSEI system can provide a cross-sectional image of a sub-100 nm non-uniform thin film object deposited on a warped substrate. This unique measurement capability is enabled by combining spectral interferometry (SI) with dynamic spectroscopic imaging ellipsometry (DSIE) employing a monolithic spectral polarizing interferometric module. In this study, we present a method for obtaining a real cross-sectional thickness line profile by compensating for the nonlinear phase term introduced by the ultra-thin film. To evaluate the effectiveness of the proposed compensation method and measurement reliability, a SiO₂/Si step-shape sample is measured and analyzed. We demonstrate that the proposed DSEI system can provide non-uniform thin film thickness and substrate warpage profiles with nanometer-level vertical resolution and a large field of view of 10 mm.