Phase Shifting Imaging Ellipsometer

• Main Authors: Ching-hung Hung, 洪青宏
• Other Authors: Kuei-chu Hsu
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/44045714315676809427

碩士 === 國立中央大學 === 光電科學研究所 === 99 === In this thesis, a phase shifting imaging ellipsometer (PSIE) is developed and set up for two-dimensionally measuring ellipsometric parameters of a tested specimen. In the optical setup of the PSIE, a liquid crystal variable retarder (LCVR) is employed to change the phase retardation at high speed. The phase retardation adjustment of an LCVR, plays an important role in phase-shifting technique, where the phase retardation is dependent upon the applied voltage of modulation signal. We also propose a calibration process to accurately determine the applied voltages relative to the specific retardations. Therefore, the spatial distributions of the ellipsometric parameters can be calculated through the intensity images of phase shifting transformation, acquired by a CCD camera. PSIE has ability to to measure the physical properties of both isotropic and anisotropic materials. This is one of the features of our developed system. We give the experimental verifications for characterizing them, which are done by (1) measuring the thickness distribution of a SiO2 thin film on the Si substrate and (2) measuring the twisted angle and cell thickness of a twisted nematic liquid crystal cell, as the experimental demonstration for an isotropic and an anisotropic materials. The experimental results are all close to the given values, shown that the correctness of our theory and measurement accuracy.