Quantitative Phase Imaging of Thin Film Surface

Abstract

In this study, the white light diffraction phase microscopy and the generalized Morse wavelet are proposed to achieve practical and precise measurement of a thin film surface. The white light diffraction phase microscopy provides low speckle noise and single-shot measurement, and thus it has been used to produce an image with interference fringes from the surface of a thin film. Relying on produced interferogram, quantitative phase information of the thin film surface has been obtained using the continuous wavelet transform. In the calculation of the quantitative phase, in many studies the continuous wavelet transform method with different wavelets is preferred. The Morlet wavelet is a commonly used one with a fixed resolution. An alternative approach is proposed using the generalized Morse wavelet capable of controlling the resolution. It has an additional advantage of varying the two parameters, thus improving the sensitivity of phase calculation. Results of the generalized Morse wavelet were compared with the Morlet and Paul wavelets which also have one varying parameter. For the determination of the thin film surface profile, besides the white light diffraction phase microscopy, surfaces have been investigated by a Dektak stylus profilometer and a scanning electron microscope. In this way, it was possible to observe the difference between the most commonly used methods with regard to the imaging of thin film surfaces. The application of the white light diffraction phase microscopy with the generalized Morse wavelet was compared with the common microscopy techniques for studying thin film surfaces, and experimental results were discussed at the end of the study.