橢圓偏振術是量測待測樣本表面反射光或是穿透光之偏振態去分析該物質的光學特性。在各式橢圓儀的系統架設之中，干涉式橢圓儀是以振幅分光式干涉儀為基礎的量測系統，具有很高的橢偏參數量測精準度。然而，干涉式橢圓儀的實用性不若採用傳統偏振片―補償片―待測樣本―析光片架設的橢圓儀的原因有以下三點： 1. 振幅分光式干涉儀對相位的靈敏度相當高，因此干涉式橢圓儀必須維持系統的穩定性以降低外在環境的擾動所造成的影響。 2. 干涉式橢圓儀通常使用瓊斯矩陣來做理論分析而非穆勒矩陣，以致無法分析具有去偏振特性的待測樣本。 3. 在待測樣本尚未置至入之前，光學系統必須進行校正的步驟。 為了改進上述傳統干涉式橢圓儀的缺點，本論文提出由共光程外差干涉儀結合橢圓偏光術所構成的共光程干涉式橢圓儀系統架設。共光程外差干涉式橢圓儀所使用光源是能夠同時發射兩道正交，且帶有不同頻率之線偏振光的雙頻雷射。利用共光程組態可以大幅消除環境所引起的雜訊干擾，由於光程外差干涉式橢圓儀可適用於穆勒矩陣和史托克向量來做理論分析，適用於分析去偏振樣本。同時不需要額外的系統校正步驟，因此可以達到高精度橢圓參數即時量測之目的。 本論文共提出並架設三種的不同型態的共光程外差干涉式橢圓儀的量測系統： 1. 第一個系統架設是高速線性偏振調變橢圓儀。它是結合線性偏振旋轉器以及共光程外差干涉儀來量測橢偏參數。高速線性偏振調變橢圓儀具有精確且即時量測橢偏參數的能力；在量測矽基材上的二氧化矽薄膜厚度可以達到1 nm的精確度。 2. 第二個系統架設是雙頻成對偏振相移式橢圓儀，它結合了共光程外差干涉儀與相移干涉術，經由實驗結果可以證實雙頻成對偏振相移式橢圓儀同時具有精確量測橢偏參數以及完整的橢偏參數的動態範圍的能力。 3. 第三個系統架設是光學同調橢圓儀，它是由雙頻線性雷射光結合共光程外差干涉儀所組成。光學同調橢圓儀可以精準地量測去偏振樣本的橢偏參數。同時亦可以量測雷射光的偏振度以及同調度。 Ellipsometer belongs to a technique that is able to characterize the optical properties of a tested specimen by measuring the polarization state of light reflected from or transmitted through its surface. Among different kinds of the ellipsometers, interferometric ellipsometer (IE) is based on an amplitude division interferometer and is able to measure the ellipsometric parameters at high precision. However, IE is not popular than conventional ellipsometers which are based on polarizer-compensator-specimen-analyzer (PCSA) configuration because of the following reasons: 1. The amplitude-division interferometer is highly sensitive to phase noise. Then IE needs to be maintained at high stability in order to reduce the phase influence from surroundings. 2. The working principle is commonly described by use of Jones calculus rather than Mueller matrix so that IE can not be utilized to characterize a depolarizing specimen. 3. IE is required calibration prior to tested specimen being measured. In order to overcome the disadvantages of the conventional IE, a common-path heterodyne interferometric ellipsometer (CHIE) by integrating the conventional ellipsometer with the common-path heterodyne interferometer is proposed and set up in this thesis. A dual-frequency laser which emits two orthogonally linearly polarized laser lights with slightly temporal frequency difference is served as a light source in CHIE. The background phase noise can be eliminated effectively by utilizing the common-path configuration. Since CHIE can be described by Mueller matrix, hence it can characterize a depolarizing specimen. The system calibration is not necessary in CHIE either, thus the ellipsometric parameters can be measured in real time with high accuracy. In this thesis, three different system setups of CHIE are proposed: 1. The first system setup is a high-speed linear polarization modulation ellipsometer. It is based on a linear polarization rotator and is integrated with a common path heterodyne interferometer for ellipsometric parameter measurement. A real-time and accurate measurement of ellipsometric parameters, which demonstrated an accuracy of less than 1nm on thickness of SiO2 thin film deposited on silicon substrate, was verified experimentally. 2. The second system setup is a dual-frequency paired polarization phase shifting ellipsometer. It combines the features of the phase shifting interferometer and common-path heterodyne interferometer where the ellipsometric parameters of a specimen are measured accurately. The experimental results verify that dual-frequency paired polarization phase shifting ellipsometer is capable of determining the full dynamic range on ellipsometric parameters. 3. The third system setup is an optical coherent ellipsometer, in which a dual-frequency linearly polarized laser beam is integrated with a common-path heterodyne interferometer. Optical coherent ellipsometer is able to precisely measure the optical properties of a depolarizing specimen by measuring ellipsometric parameters. In the mean time, the degree of polarization and the degree of coherence of incident dual-frequency linearly polarized laser beam are measured too.
