Measurement of Film Structure Using Time-Frequency-Domain Fitting and White-Light Scanning Interferometry

Abstract

A new technique is proposed for measuring film structure based on the combination of time- and frequency-domain fitting and white-light scanning interferometry. The approach requires only single scanning and employs a fitting method to obtain the film thickness and the upper surface height in the frequency and time domains, respectively. The cross-correlation function is applied to obtain the initial value of the upper surface height, thereby making the fitting process more accurate. Standard films (SiO2) with different thicknesses were measured to verify the accuracy and reliability of the proposed method, and the three-dimensional topographies of the upper and lower surfaces of the films were reconstructed.

Keywords

• white-light vertical scanning interferometer
• Fourier transform
• Michelson interferometer
• nonlinear fitting
• cross-correlation function