MOCVD噴淋式腔體沉積模擬與進氣系統分析

游翔霖(Siang-Lin You)

指導教授 ： 洪銘聰

國立中央大學/工學院/機械工程學系/碩士(2014年)

摘要

金屬有機化學氣相磊晶(metalorganic chemical vapor deposition, MOCVD)技術廣泛使用於LED磊晶生長，目前市面上主要的MOCVD設備包括TurboDisc、行星式與近耦合噴淋式，每種機台皆有其優缺點。近耦合噴淋式腔體具有良好的沈積均勻性與反應氣體使用率，由於進氣系統會受到預反應影響，導致噴嘴處容易產生堵塞的現象而影響磊晶生長，必須定期清理避免磊晶生長受到影響。本研究針對近耦合噴淋式腔體之沈積與噴嘴堵塞情形進行研究，利用有限元素法進行數值模擬。模擬中考量腔體內熱流場、質量傳輸及化學反應之耦合，並針對反應過程產生的各物種之濃度分佈及其對沈積貢獻度進行深入探討。研究中除了建立磊晶成長與噴嘴堵塞評估機制，並針對噴嘴進行改善設計，以減少噴嘴處沈積改善噴嘴阻塞。研究結果顯示在化學反應影響下，噴嘴處的物種以TMG(trimethyl gallium)與加合物(adduct)為主；載盤處的物種以MMG(monomehyl gallium)為主；而DMGNH2(dimethyl gallium amide)在腔體中生成的量極少。在進氣流速與比例影響分析中，流速增加會造成載盤處長率提高、噴嘴處長率下降；TMG質量分率提高則載盤長率與噴嘴的沉積都會增加。最後進行進氣設計改良分析，分別在噴嘴處加入阻擋物與倒角，當阻擋物長度增加，載盤長率會提升，噴嘴沉積會減少，但會造成磊晶均勻性降低。當倒角長度增加，載盤長率略為下降，噴嘴處進口的沉積減少。

關鍵字

數值模擬 ； MOCVD ； 近耦合噴淋式腔體

並列摘要

Metalorganic chemical vapor deposition is widely used in LED manufacturing. There are different reactor designs on the current market including TurboDisc, planetary, and close-coupled showerhead. Close-coupled showerhead reactor has good deposition uniformity and minimum source gas usage, but it has gas inlet nozzle plugging problem. In this study, we use finite element method to simulate the reaction and physical phenomena in a close-coupled showerhead reactor and evaluate the GaN deposition uniformity and the gas inlet nozzle plugging problem. The results show that the main species in the vicinity of the inlet nozzle is TMG and TMG:NH3. While the main species near the susceptor surface is MMG. The concentration of DMGNH2 in the reactor is very low. Increasing the gas inlet velocity can increase the growth rate and reduce nozzle plugging. Increasing the mass fraction of TMG source gas results in the increase of both the growth rate and nozzle plugging, but it is less significant on the plugging problem. Finally, we modified the inlet nozzles with barriers and chamfers.We found that the epitaxial growth increases and the nozzle plugging reduces with increasing barrier length. In the chamfering design, we found both the epitaxial growth and the nozzle plugging reduce with increasing chamfering length.

並列關鍵字

numerical simulation ； MOCVD ； close-coupled showerhead

參考文獻

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