Measurement of Refractive Index and Thickness of Fluorinated Copolyimide Films by Spectroscopic Reflectometry

摘要

Various fluorinated copolyimide films were prepared on a Si wafer from copoly(amic acid) solution of pyromellitic dianhydride (PMDA) or bis(3,4-dicarboxyliphenyl)hexafluoropropane dianhydride (6FDA) and a diamine mixture of 4,4'-oxydianiline (ODA) and 2,2'-bis-(trifluoromethyl)benzidine (BTBz). Refractive index and thickness of polyimide films were measured by means of spectral reflectance measurement. A gradual increase of the refractive index was observed in the course of imidization for PMDA aeries polyimides and almost no change or a slight decrease for 6FDA series polyimides. Film thickness decreased about 30 percent after imidization. The refractive indices of final polyimides depended on the fluorine content as well as the structure of the copolyimide.