臺灣博碩士論文加值系統

摘要
MOCVD製程是半導體製程中重要的一環，而且可應用在太陽能電池上，其製程之好壞關係到整個太陽能電池之效率，因此本研究分析改善其沈積品質。
本研究利用計算流體力學(CFD)中的SIMPLE法來計算MOCVD之流場過程，分析其速度場、溫度場以及濃度場之狀態，配合前人實驗來對照並且分析模擬出更佳之設計。
本文主要探討出口之效應對於GaAs沈積效果之影響，分析在不同的出口大小和位置對於其沈積速率與均勻度之影響。此外，本文還討論入口與晶座之距離、入口速度以及晶座寬度對於沈積速率與薄膜均勻度之差異。
結果得知，出口方向會影響GaAs之沈積率與薄膜均勻度，當出口為橫向側抽時，其薄膜均勻度最佳。就出口大小而言，當出口縮小時會造成晶座兩端速度增快，降低了整體薄膜沈積之均勻度，由此可知，對於沈積薄膜，控制速度邊界層是非常重要的。同時本研究發現入口速度、晶座寬度與入口至晶座之距離皆會影響沈積速率和薄膜均勻度，而其中影響最大之因素為入口至晶座之距離，因為從葛瑞秀夫數(Grashof number)可知，h為三次方之變數。
本研究利用數值模擬配合前人實驗的結果來分析影響MOCVD沈積之變數，發現出口位置與大小對於GaAs之沈積有一定的影響，而本文模擬出最佳結果為全入口，流速Re值小於100，晶座與入口距離為180mm，出口方向為橫向側抽。

Abstract
A method using CFD-based computer simulations as a virtual reactor was proposed for cost-effective CVD reactor design. The virtual reactor was developed by combining the chemical reactor mechanism and rate constants obtained from kinetic studies using a small-scale, with the momentum, mass and heat transport processes simulated using a CFD code. The effect of the flow structure on the film thickness uniformity is demonstrated for the growth of GaAs from a Ga(CH3)3 -AsH3- H2 mixture.
We present a modeling study of the growth of gallium arsenide layers deposited onto a high-temperature susceptor in a cylindrical metalorganic chemical vapor deposition reactor. We analyzed the deposition process with a two-dimensional model that is axisymmetric about the vertical axis.
We attempted to control the extent of the consecutive reaction by modifying the flow pattern. For the output of side walls, because the gas velocity increase near the wafer edge, the residence time was lower in the central part of the wafer than near the edge. Therefore, it can be controlled by locating the outlet such that residence time above the entire wafer is uniform.
And the study finds that decreasing the hole size lowered the film uniformity. This occurred because relative to the velocity at the center of the wafer, the velocity near the wafer edge increased with decreasing hole size. This result confirms that the control of the boundary layer thickness is very important for the film thickness uniformity. We also find that decreasing the shower-to-wafer distance increased velocity near the wafer and therefore increased the growth rate.
The present study indicates that we can design a MOCVD reactor and optimize the operating conditions efficiently using a computer simulation with other’s experiments.

目錄
目錄………………………………………………………………………I
圖目錄Ⅲ
表目錄Ⅴ
論文摘要（中文）Ⅵ
論文摘要（英文）Ⅶ
符號說明Ⅷ
第一章 緒論1
1.1 研究背景與動機1
1.2文獻回顧3
1.3 研究內容7
第二章 理論模式11
2.1薄膜沈積原理11
2.2化學氣相沈積(CVD)反應步驟14
2.3化學氣相沈積(CVD)之種類15
2.4影響薄膜成長之因素……………………………………………15
2-4-1 動量傳輸16
2-4-2 熱能傳遞16
2-4-3 質量傳送16
2-4-4 化學氣相沈積(CVD)動力學16
2.5 GaAs製程之數值模擬………………………………………..16
2.6統御方程式………………………………………………………19
2.7 無因次化……………………………………………………….20
2.8 流體輸送性質………………………………………………….22
2-8-1 黏度(Viscosity)…………………………………………..22
2-8-2 熱傳導系數 (Thermal conductivity)……………………23
2-8-3 質傳系數(Mass diffusivity)…………………………….23
2-8-4 氣體密度(gas density)……………………………………23
第三章 數值模擬方法27
3.1交錯網格與控制體積27
3.2 SIMPLE演算法之理論模式28
3.2.1有限體積數值模擬方法簡介…………………………………28
3.2.2格點的配置……………………….………………………….29
3.3 SIMPLE之數值計算方式29
3.3.1動量離散方程式…………………………….……………….29
3.3.2 SIMPLE法的解題步驟……………………………………...31
3.4收斂條件31
3.5誤差標準設定32
3.6 邊界條件33
3.6.1 原始邊界條件………………………………………………33
3.6.2 無因次化邊界條件…………………………………………34
3.7求解流程……………………………………………………….36
第四章 數值模擬結果與分析38
4.1 研究內容38
4.2 縱向出口大小39
4.3 縱向出口位置40
4.4 橫向側抽之探討41
4.5 縱向與橫向出口比較42
4.6 入口與晶座間距離43
4.7 晶座面積之影響43
4.8 入口速度變化影響44
第五章 結論與建議75
5.1 本文結論75
5.2未來展望76
參考文獻77

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