金屬有機氣相沉積反應腔體之熱流場與質傳數值模擬分析

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題名:	金屬有機氣相沉積反應腔體之熱流場與質傳數值模擬分析
作者:	莊博安;Chuang,Po-an
貢獻者:	能源工程研究所
關鍵詞:	金屬有機氣相沉積法;熱流場與質傳數值模擬;Metal-organic chemical vapor deposition;MOCVD
日期:	2013-07-24
上傳時間:	2013-08-22 12:03:18 (UTC+8)
出版者:	國立中央大學
摘要:	摘要有機金屬化學氣相沉積法(MOCVD)是發光二極體(LED)製程中，生長半導體薄膜的一種方法，而膜厚的均勻性與成長速率攸關LED效率與品質。本研究採用VEECO E400LDM垂直式反應腔體進行模擬，並探討狹長式入口分佈及熱流場與物質傳輸現象。本研究首先建立化學反應機制，當三甲基鎵(TMG)與氨氣分別通入反應腔體時，三甲基鎵與氨氣會隨著溫度變化產生一連串不同的反應路徑，本研究製程溫度為1000K為質量傳輸限制的條件下，沉積速率取決於氣相反應中三甲基鎵(TMG)的熱裂解，裂解成雙甲基鎵(DMG)與單甲基鎵(MMG)，在基板面上反應速率為單甲基鎵(MMG)遠快於DMG與TMG，因此藉由Fick’s law 計算MMG的沉積速率。接著本研究假設氨氣已均勻混合的情況下通入載流氣體與三甲基鎵，探討排列狹縫式入口的數量、狹縫式入口的寬度、狹縫式入口對應載盤的範圍。我們發現(1)當狹縫入口少於11條時，入口與入口間會有迴流產生(2)流量固定下，入口寬度改變時，對均勻性影響不大(3)當狹縫是入口範圍對應載盤向內縮時，整體成長速率提升，較均勻的區域以縮至直徑範圍0.43m均勻性為最佳。接著將狹縫入口分區段，入口分別通入載流氣體、TMG與氨氣，探討氣體混合的機制，由於載流氣體的密度與氨氣相差很大，所以我們必須調整進氣口流速使腔體內的流場均勻。當整體流速變小或入口溫度提高時，有助於提升反應氣體間擴散與均勻性。當載盤轉速增加時，對旋轉半徑大的區域速度越快，均勻的效果較好，載盤中心則受到停滯流影響，濃度較無法受旋轉氣流帶開。經過本研究探討，若要提升均勻性除了必須達到流場均勻外，必須提升反應氣體間的擴散作用，使反應氣體均勻分佈在載盤上。 Abstract Metal organic chemical vapor deposition (MOCVD) manufacturing process of light emitting diode (LED) is a method of growing thin film on semiconductor. The uniformity of the film thickness is relevant to LED efficiency and quality. This study uses VEECO E400LDM vertical reaction chamber model to simulate and investigate the arrangement of slot jet as well as thermal-fluidic fields and mass transfer phenomena. This study first built the mechanism of chemical reaction. When TMG and Ammonia gas were introduced into the reaction chamber individually, TMG and Ammonia were to react and generated a series of different reaction paths vary with temperature. In this study, the process temperature is 1000K in the mass transfer limited region. The deposition rate depends on TMG decomposition in gas phase reaction. TMG will decompose to DMG and MMG. The reaction rate of MMG is far faster than TMG and DMG in the surface of substrate. Therefore we calculated MMG deposition rate by Fick’s law. Then, we assumed that ammonia has been mixed uniformly. TMG and carrier gas introduced in the chamber have investigated the number of slot jet arrangement and the wide as well as the range of slot jet corresponding to the load plate. This study found (1) When the slot jet is less than 11, it will generate the recirculation between the inlet. (2) As the width of the inlet is changed, there is the minimal effect on the uniformity in constant flow rate. (3) Since the range of slot corresponds to the load plate inward contraction, the growth rate will increase as contracting with 0.43m in diameter uniformity considered as the best one. After that, we partition off the slot jet in sections. The entrances were introduced into the carrier gas, TMG and ammonia, then investigated the mechanism of gas mixture. Because the density of the carrier gas has big difference with ammonia, we have to adjust the flow rate of the inlet to make the uniform flow field. When the overall flow rate is decreased or the inlet temperature increases, will enhance the diffusion between the reaction gas and uniformity. In addition, when the load plate speed is increased, the speed in the large radius of rotation region is much faster. Therefore, the uniformity is better. The growth rate of load plate center is higher due to flow stagnation point. According to this study, in order to obtain better uniformity, not only the flow field must be uniform but also improve the diffusion of the reaction gas, let the reaction gas distributed uniformly on the load plate.
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