本論文中針對三氯矽甲烷(MTS)為原料在氫氣氣氛下化學氣相沉積β相碳化矽薄膜的反應機制進行量化模型之探討。首先以一簡化的模型，即僅考慮MTS氣相解離生成一中間產物並貢獻長膜的逐次反應型式，對熱壁式水平圓管反應器內隨著反應滯留時間方向的薄膜成長速率分布數據進行模型擬合。對於改變反應管溫度由950到1050°C時均溫區域段0.5 s滯留時間內的量論組成碳化矽長膜的模型擬合結果發現，決定長膜速率的第一步驟確實為MTS的氣相解離反應(活化能約67 kcal/mol)，又生成的中間產物之表觀表面附著機率隨反應溫度升高由5.5 × 10-4增加到8.9 × 10-4 (活化能約17.2 kcal/mol)，顯示出中間產物擴散到基材表面後的表面反應為控制長膜的第二步驟。
進一步對於不同[H2]/[MTS]進料濃度比下水平圓管反應器內隨著反應滯留時間方向的薄膜成長速率分布進行模型擬合後發現，三氯矽甲烷與氫氣在氣相中的逐次反應對氫氣濃度呈0.5次方的反應次數，顯示反應物在氣相中至少生成兩種氣態中間體，分別對應之表面附著機率為4.6×10-4和5.1×10-2，並同時貢獻於碳化矽的薄膜成長。我們輔以量子化學模擬原料之間的氣相分解反應發現，三氯矽甲烷可能先氣相解離掉氯化氫形成具π鍵的1,1-二氯矽烷分子(對應到較小的附著機率)，之後與氫氣產生自由基鏈鎖反應並脫氯形成自由基物種(對應到較大的附著機率)。而這些氣相中間體持恆的1:1碳矽原子比應為導致當量組成碳化矽薄膜生成的主要原因。

This paper investigates the modeling of the reaction mechanism for the chemical vapor deposition of beta-phase silicon carbide films using methyltrichlorosilane (MTS) as the precursor in a hydrogen ambiance. Initially, a simplified model was employed, considering only the gas-phase dissociation of MTS to produce an intermediate species and its consecutive reactions contributing to the film growth rate along the direction of the reaction residence time in a hot-wall horizontal tube reactor. The model was fitted to the experimental data of the film growth rate distribution under varying reaction temperatures from 950 to 1050°C, with a residence time of 0.5 s in the uniform temperature zone. The results of the model fitting revealed that the first step determining the film growth rate is indeed the gas-phase dissociation of MTS (activation energy approximately 67 kcal/mol). The apparent sticking probability of the intermediate species increased from 5.5 × 10-4 to 8.9 × 10-4 as the reaction temperature increased (activation energy approximately 17.2 kcal/mol), indicating that the surface reaction of the intermediate species after diffusing to the substrate surface controls the second step of film growth.
Furthermore, the model was fitted to the experimental data of the film growth rate dis-tribution along the direction of the reaction residence time in the horizontal tube reactor under different [H2]/[MTS] feed concentration ratios. It was found that the consecutive reactions of MTS and hydrogen in the gas phase exhibit a reaction order of 0.5 with respect to the hydrogen concentration, suggesting that at least two gaseous intermediate species are formed during the reaction, corresponding to surface attachment probabilities of 4.6 × 10-4 and 5.1 × 10-2, respectively, both contributing to the growth of silicon carbide films. Quantum chemical simulations of the gas-phase decomposition reactions of the precursors indicated that MTS likely undergoes gas-phase dissociation to form π-bonded 1,1-dichlorosilane molecules (corresponding to the smaller sticking probability) and subsequently undergoes free radical chain reactions with hydrogen, leading to chlorine detachment and the formation of free radical species (corresponding to the larger sticking probability). These gaseous intermediates maintain a constant 1:1 carbon-to-silicon atomic ratio, which is likely the main reason for the deposition of silicon carbide films with the desired stoichiometric composition.

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