氫原子和矽氫化合物(SinH2n+2，n=1~2)的反應與矽氫自由基(SinH2n+1，n=1~3)的分解反應之第一原理化學動力學研究

Abstract

氫原子跟矽氫化合物(SinH2n+2，n=1~2)的反應與矽氫自由基(SinH2n+1，n=1~3)的分解反應對於瞭解觸媒化學氣相沉積法(Cat－CVD)和電漿輔助氣相沉積法(PE－CVD)的化學反應過程是相當重要的。本研究將藉由ab initio分子軌域與化學反應動力學的理論計算來探討這些反應。在第一部分的研究，我們必須確認這些經由計算後所獲得到的反應熱以及更進一步地也考慮計算isodesmic reactions的反應熱，例如: SiH+CH4→SiH4+CH，SiH3+CH4→SiH4 + CH3，Si2H5+C2H6 → Si2H6+C2H5等等，這些反應熱將利用於預測某些矽氫化合物得化學反應生成熱，同時與現有文獻的實驗數據做為比較。最後利用TST理論配合Eckart非對稱的位能曲面的方法去計算氫原子與矽氫化合物的反應速率常數。另一方面，與矽氫自由基熱分解相關的反應速率常數將使用CVTST或RRKM theory with master equation 或VTST的理論方法做為計算。而這些理論計算的結果將預測在適當的溫度和壓力範圍內，並且與相關的實驗數據作為比較及驗證。

The reactions of hydrogen atoms with silicon hydrides (SinH2n+2, n=1~2) and the decomposition reactions of silicon hydride radicals (SinH2n+1, n=1~3) are relevant to the understanding of catalytic chemical vapor deposition (Cat-CVD) and plasma enhanced chemical vapor deposition (PECVD) processes. In the present proposed study, these reactions are investigated by means of ab initio molecular-orbital and chemical kinetics theoretical calculations. In the first phase of the study, we validate the calculated enthalpies of the reaction by considering further isodesmic reactions, such as SiH+CH4→SiH4+CH, SiH3+CH4→SiH4+CH3, Si2H5+C2H6→Si2H6+C2H5 and so forth; additionally, the predicted enthalpies of the formation for essential compounds are compared with the available experimental data. Finally, transition state theory (TST) with unsymmetrical Eckart potential energy barriers is employed to obtain the rate coefficients of the hydrogen abstraction reaction. Rate coefficients relevant to the thermal decomposition reaction of silicon hydride radicals are calculated by employing canonical variational transition state theory (CVTST), the Rice-Ramsperger-Kassel-Marcus (RRKM) theory with master equation or variational transition-state theory (VTST). These rate coefficients are not only predicted in the practical ranges of temperature and pressure but are also compared with the available experimental results wherever possible.