New method of thin-film thickness measurement in wavelength scanning interferometry

Thickness of thin film measurement is a important information for the TFT-LCD and semiconductor process, ranging from spectro-photometry to interferometry. In particular many efforts have been devoted for development of measurement system to obtain thickness and surface profile. In this paper, we propose a new method by using wavelet transform to retrieve the phase information, and we demonstrate, with both theoretical and experimental data, that this method provides a reliable technique for retrieving phase in the wavelength scanning interferomety. Also we show that the proposed method can reconstruct the non linear phase better than other methods such as the conventional fourier transform and direct spectral phase calculation method. In the experimental data, we verify that the error of measurement using proposed method is less than those other methods. The patterned thin film is measured with the proposed method to obtain the thickness profile and surface profile simultaneously, demonstrating higher accuracy and performance.