Phase information in coherent Fourier scatterometry

Abstract

Incoherent Optical Scatterometry (IOS) is widely used in semiconductor industry in applications related to optical metrology particularly in grating reconstruction. Recently, Coherent Fourier Scatterometry (CFS) has emerged as a strong alternative to the traditional IOS under suitable condition. When available, phase information is an added advantage in CFS to complement the intensity data. Phase information in the scattered far field is dependent on the structure and the composition of the grating. We derive and discuss the phase information accessible through the CFS. Phase difference between the diffracted orders is computed and the polarization dependent phase sensitivity of the grating parameters are discussed. The results are rigorously simulated and an experimental implementation of CFS demonstrates the functionality of the method.