論文作者為雷射干涉重力波天文台合作組織之研究成員，研究主要聚焦於開 發下一代低溫重力波偵測器所需之鏡面鍍膜材料。目前的偵測器 (如 Advanced LIGO) 在 40–500Hz 頻段受限於塗層布朗熱噪聲 (Coating Brownian Noise)。為降 低此雜訊，未來偵測器如 LIGO Voyager、CHRONOS 以及愛因斯坦望遠 (Einstein Telescope) 計畫採用矽基鏡面鍍膜，於低溫環境下操作，並且使用 1550–2000nm 之雷射波長。這些鍍膜之光學吸收率必須低於 1ppm，遠低於現有鍍膜技術所能 穩定達成的目標。 我們利用台灣半導體研究中心 (TSRI) 之低壓化學氣相沉積 (LPCVD) 系統， 與中央研究院 (AS) 及國立清華大學 (NTHU) 合作，製作非晶矽 (a-Si)、氮化 矽 (SiNx) 及氮氧化矽 (SiOxNy) 薄膜。薄膜厚度與折射率由 M2000 橢圓偏振 儀量測，光學吸收率則是從史丹佛大學那邊借用高靈敏度光熱共路徑干涉儀 (Photothermal Common-path Interferometry， 簡稱 PCI) 系統進行量測。 研究結果顯示，薄膜之光學吸收率與其化學計量比密切相關。對於氮化矽 薄膜，豐富的氮含量且低氫含量之組成可產生較寬之光學能隙，從而降低吸收 率。對於氮氧化矽薄膜，增加氧含量可進一步降低吸收率。本研究中最佳結果 為 SiO1.26N0.23H0.01 薄膜，其在 1550nm 波長下之光學吸收率達到 1.29ppm，已接近下一代偵測器所要求之 < 1ppm 目標。此外，LPCVD 製作之非晶矽薄膜在1550nm 之折射率高達 n ≈ 3.66230，使其成為多層布拉格反射鏡 (Bragg mirror)中極具潛力的高折射率材料。 在製程方面，我們設計了適用於 LPCVD 之 1 吋晶圓夾具及適用於濕式蝕刻 槽之 1 吋與 3 吋晶圓夾具，並採用單面拋光 (Single-Side Polishing， 簡稱 SSP) 製 程解決 LPCVD 雙面沉積之問題。這些製程解決方案為未來重力波偵測器之高品 質鍍膜製作奠定了重要基礎。;As a member of the LIGO Scientific Collaboration， this study focuses on developing mirror coating materials for next-generation cryogenic gravitational wave detectors. Current detectors like Advanced LIGO are limited by coating Brownian noise in the 40–500Hz frequency band. To reduce this noise， future detectors such as LIGO Voyager， CHRONOS， and the Einstein Telescope plan to use silicon-based mirror coatings that operate at cryogenic temperatures and at wavelengths of 1550–2000nm. These coatings must have an optical absorption below 1 ppm， which is much lower than what current coating technologies can reliably achieve. In this study， we fabricated amorphous silicon(a-Si)， silicon nitride(SiNx)， and silicon oxynitride(SiOxNy) films using Low-Pressure Chemical Vapor Deposition(LPCVD) at the Taiwan Semiconductor Research Institute(TSRI)， in collaboration with Academia Sinica(AS) and National Tsing Hua University(NTHU). The film thickness and refractive index were measured by M2000 Ellipsometer， and the optical absorption was measured by a high-sensitivity photothermal common-path interferometer(PCI) system borrowed from Stanford University. The results show that the optical absorption of the films is strongly controlled by their stoichiometry. For SiNx films， a nitrogen-rich and lower hydrogen composition gives a wider optical band gap and lower absorption. For SiOxNy films， increasing the oxygen content further reduces absorption. The best result in this study was achieved by the oxygen-rich SiO1.26N0.23H0.01 film， which achieved an optical absorption of 1.29 ppm at 1550nm. This result is close to the < 1ppm target for next-generation detectors. In addition， the LPCVD a-Si film achieved a high refractive index of n ≈ 3.66230 at 1550nm， which makes it a promising high-index material for multilayer Bragg mirror coatings. During fabrication， we also designed new jig for 1-inch wafers for LPCVD and 1 & 3 inch jigs for wet bench， then adopted a single-side polishing(SSP) process to solve the backside deposition problem in LPCVD. These engineering solutions are important steps toward producing high-quality coatings for future gravitational wave detectors.
