噴流式MOCVD腔體之熱流及質傳研究分析;Analysis of thermal flow and mass transport in MOCVD round jet chamber

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Title:	噴流式MOCVD腔體之熱流及質傳研究分析;Analysis of thermal flow and mass transport in MOCVD round jet chamber
Authors:	劉正皓;Liu,Cheng-Hao
Contributors:	機械工程學系
Keywords:	有機金屬化學氣相沉積法;氮化鎵;流場分析;導流板設計;MOCVD;GaN;Flow field analysis;Deflector design
Date:	2016-08-18
Issue Date:	2016-10-13 14:55:51 (UTC+8)
Publisher:	國立中央大學
Abstract:	金屬有機化學氣相沉積法（MOCVD）技術由於具有外延層(epitaxial layer)均勻性較好、材料純度高等優點，為現今LED磊晶產業用於生長氮化鎵的重要製程技術。本研究利用有限元素分析法(FEM)與實驗比較，為使生長速率計算更接近實際製程，同時考慮物種由於質傳與表面反應造成的反應消耗。利用數值模擬，藉由Langmuir熱力學定理計算氣相反應後各物種在晶圓表面上的吸附速率，並以MMG作為主要的吸附物種，主要的反應式共有1條。先解決round jet 入口過於單純，並將slot jet入口運用在導流板設計，為改善入口流速為目標，對於整體腔體內部流場做分析，並從實驗與模擬作比對，確認模擬真實性，並朝著適合薄膜生長的製程參數情形下，做模擬分析。模擬結果顯示，增加進氣流量使得氣體濃度容易朝slot jet中心集中，造成因慣性力而產生的渦旋變強。而最好入口流速的雷諾數為2~3之間；增加載盤溫度會使入口與載盤間的溫度梯度升高，Rij超過5000時，在載盤附近會開始有熱浮力產生的渦旋來影響流場；增加載盤旋轉可明顯抑制熱浮力的效應，而抑制熱浮力所導致的渦旋。Riw約為0.05時，能有效的抑制熱渦旋。增加壓力有利於增加成長速率，但相對的流場變為難以控制，流場不穩定容易造成均勻性不佳。接下來修改出口設計，對基本幾何參數與出口幾何參數進行設計，結果顯示將出口加寬為27.5mm時，並修正單孔狀出口，變為環狀出口時，能夠達到較好的入口均勻性，整體流場也變為plug flow。 ;Metalorganic chemical vapour deposition (MOCVD), with it advantages as better epitaxial layer and high material purity, is a vital process technique for GaN growth in the LED Epitaxy industry.The finite element analysis (FEM) was employed in the current study for experimental comparison, aiming to make the growth rate more close to actual processes and take into account the reaction depletion resulting from the reaction of mass transfer on the surface.The Langmuir equation was adopted to calculate the absorption rate on wafer surfaces among species after the vapor reaction. In addition, MMG was used as the major absorbed species,with one major reaction equation.Over simplicity of round jet was solved first and the slot jet was then applied to the design of deflectors.To improve the inlet flow rate, the flow field analysis on overall chambers was carried out and compared against the simulation to make sure the authenticity of the simulation,with relevant simulation analysis implemented in conditions appropriate for the growth of the thin film.The results of the simulation revealed that the increase in the intake flow rate enabled the gas concentration to move towards the center of the slot jet,making the vortex as the result of inertia even stronger. The optimal Reynolds number of the inlet flow rate should be between 2 and 3. Increase in the carrier plate temperature made the temperature gradient between the inlet and the carrier plate higher.When Rij reached over 5000, vortexes resulting from thermal buoyancy appeared around the carrier plate and affected the flow field.The increase in carrier plate spin significantly inhibited the effect of thermal buoyancy and thus the resulting vortexes.When Rjw was 0.05, thermal vortexes could be effectively inhibited.The increase in pressure was beneficial to growth rate, yet the flow field became much uncontrollable.Unstable flow field easily led to poor evenness.The next step was modifying the outlet based on basic geometrical parameter and outlet geometric parameter.The results indicated that when the outlet was widened to 27.5mm and changed to round style rather than its original single-hole style, better inlet evenness could be obtained and the overall flow field became plug flow.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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