應用於鑽石鍍膜之電容式電漿輔助化學氣相沉積之甲烷/氫氣電漿數值模擬

Numerical analysis on the methane/hydrogen plasma in a capacity-coupled PECVD reactor applied for diamond deposition

呂培煒(Pei-Wei Lu)

指導教授 ： 王訓忠

國立清華大學/工學院/動力機械工程學系/碩士(2017年)

摘要

本研究使用商用軟體CFD-ACE+，以流體模型模擬電容耦合式電漿輔助化學氣相沉積法沉積鑽石薄膜。基於簡化分析，腔體溫度設為等溫；模擬中不考慮成長薄膜之表面反應，僅以吸附係數(sticking coefficient)定義物種撞擊壁面之通量；且假設一旦正離子撞擊壁面，即形成中性粒子返回至腔體。
　　首先，將本研究之數值結果與文獻比對，以確定本數值分析的可靠性。採用之化學反應方程組為根據不同文獻資料並加以改良，此過程根據腔體內電漿放電特性，觀察電子密度、電子溫度、各粒子密度等參數在反應室中的分佈，並且針對沉積薄膜的主要粒子：CH3、CH2、H的生成與消耗，做化學反應式之影響性分析，計算的化學反應式。接續探討不同進氣位置與不同通入CH4/H2比例的影響，發現當氣體由反應式兩旁通入時，氣體主要以擴散的方式流動至基板表面，流動速度慢，在基板上方滯留時間長，有較足夠的時間可以將甲烷分解，因此基板上方CH3密度較高；且在通入甲烷 20 sccm且氫氣 80 sccm的操作環境下，CH3在徑向上的分佈均勻，基板上方的H密度最高，預期能有較均勻的薄膜沉積，且能有效的形成sp3的鍵結而獲得較佳品質的鑽石沉積薄膜。最後，分析不同腔體溫度(300K、400K、500K)對反應室內各物種濃度的影響，發現隨著溫度升高，物種濃度有明顯的下降，因此認為腔體溫度效應不宜忽略。

關鍵字

電漿 ； 數值模擬 ； 鑽石鍍膜

並列摘要

In this study, we use fluid model to simulate capacity coupled plasma enhance chemical vapor deposition using in diamond deposition with CFD-ACE+. In order to simplify the simulation, we use sticking coefficient to define the species flux to the boundary and do not consider the surface reaction when growing film. Also, we assume that when ions strike to the wall, they will absorb electrons from the wall and reflect to the chamber as neutral particles.
　　First, we compare our result with data in the literature for reliability confirmation. The reaction mechanism is determined by modifying the reaction mechanisms available in the literature. With the distributions of electron density, electron temperature, species number density in the reactor are analyzed for pure CH4 under a fixed temperature of 300 K and pressure of 300 mtorr, the most influential reactions to the generation and consumption of CH3, CH2 and H, the most influential species in diamond growth, are identified. Subsequently, the effects of different inlet arrangements and inlet CH4/H2 mixtures. When the inlet is located on the outer rim of the upper surface, slightly higher CH3 concentration is obtained above the substrate. This is because the transport process is mainly by diffusion, so that there is longer species residence time above the substrate when the gas flow enters through the outer rim. When the mixture is 20 sccm CH4 with 80 sccm H2, there can be uniform CH3 distribution with high H density above substrate so that uniform and good-quality diamond film deposition may be expected. Furthermore, analyses for different chamber temperatures (300 K, 400 K, and 500 K) reflected different chemical compositions due to the temperature effect.

並列關鍵字

plasma ； simulation ； diamond deposition

參考文獻

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