| 摘要: | 金屬有機化學氣相沉積法(MOCVD)是一種利用前驅物的反應物來源，透過加熱器使前驅物汽化，再透過載氣的輸送，在基板表面產生化學反應，進而形成一層又一層排列整齊且堆積緊密的薄膜，已經成為在生產大尺寸、複合半導體元件的主要技術，因此在現今多樣的 LED 或是半導體產業，對於生長薄膜的品質(非均勻性、長率)要求會更加嚴格。
本研究將以 GaN 薄膜的化學機制和輸送現象基礎理論知識，藉由模擬軟體數值求解，考慮會影響薄膜品質(非均勻性、長率)的因素(包含:入口之長度和口徑、腔體之壓力和轉速等)，分別探討製程參數及腔體幾何條件對於薄膜品質的關係，並且對於其中涉及之化學反應、物種傳輸及熱流場進行分析，由分析結果決定作為控制變量之參數，透過最佳化方法，最終找到 GaN 薄膜的最佳生長環境條件。
首先建立在入口處反應氣體 TMGa、NH3 及載氣 H2 同時混合之穩態模型，與文獻之實驗結果進行比對驗證，由製程參數及腔體幾何條件對於薄膜品質的關係，可以得知腔體壓力、中間進氣口徑、進氣入口長度對非均勻性、生長速率都有明顯的影響，因此決定以這三個參數作為控制變量，最後，透過COMSOL 模擬軟體與基於 Nelder-Mead 算法的優化程序集成，以獲得控制變量的最佳值。非均勻性 12.48 %減小至 5.67 %，薄膜均勻性提升 54 %；生長速率 1.83 um/h 減小至 1.52um/h，薄膜生長速率降低 17 %，由於最佳化的目標為同時考慮薄膜均勻性及生長速率，因此在整體目標函數上，得到薄膜之最適生長環境。;Metal organic chemical vapor deposition (MOCVD) is a source of reactants using precursors. The precursor is vaporized by a heater, and then transported by a carrier gas to generate a chemical reaction on the surface of the substrate, thereby forming a layer and a neat array. The densely packed film has become the main technology for producing large-size, composite semiconductor components. Therefore, in today′s diverse LED or semiconductor industries, the quality (non-uniformity, growth rate) of the grown film is more stringent.
This study will use the basic theoretical knowledge of the chemical mechanism and transport phenomena of GaN thin films to solve the factors affecting film quality (non uniformity, growth rate) by simulating software numerical values (including: length and diameter of the inlet, reactor pressure and rotational speed, etc.), respectively, to explore the relationship between process parameters and reactor geometry for film quality, and
analyze the chemical reactions, species transport and heat flow fields involved, and determine the parameters as control variables through the analysis results. The
optimization method ultimately found the optimal growth environment conditions for the GaN film.
Firstly, a steady-state model is established in which the reaction gases TMGa, NH3 and carrier gas H2 are mixed at the inlet, and the experimental results are compared with the experimental results. The relationship between the process parameters and the cavity geometry for the film quality can be known. The pressure, the intermediate inlet diameter and the inlet diameter have a significant influence on the non-uniformity and the growth rate. Therefore, it is decided to use these three parameters as the control variables. Finally, through the COMSOL simulation software and the Nelder-Mead algorithm-based optimization. Program integration to get the best value for the control variables. Non-uniformity decreased from 12.48% to 5.67%, film uniformity increased by 54%; growth rate decreased from 1.83 um/h to 1.52 um/h, and film growth rate decreased by 17%. Since the goal of optimization is to consider both the film uniformity and the growth rate, an optimum growth environment of the film is obtained on the overall objective function. |
