Spectral interferometric technique to measure the relative phase change on reflection from a thin-film structure

摘要

A two-step white-light spectral interferometrictechnique to measure the relative phase change on reflectionfrom a thin-film structure is presented. The technique isbased on recording of the channeled spectra at the output ofa Michelson interferometer and their processing by using awindowed Fourier transform to retrieve the phase functions.In the first step, the phase difference between the beamsof the interferometer with a thin-film structure is retrieved.In the second step, the structure is replaced by a referencesample of known phase change on reflection and the correspondingphase difference is retrieved. From the two phasedifferences, the relative phase change on reflection from thethin-film structure is obtained. The feasibility of the simplemethod is confirmed in processing the experimental data fora SiO2 thin film on a Si wafer of known optical constants.Four samples of the thin film are used and their thicknessesare determined. The thicknesses obtained are compared withthose resulting from reflectometric measurements, and goodagreement is confirmed.