化学气相沉积碳化硅的热力学分析

根据吉布斯自由能最小原理, 采用FACTSAGE计算软件, 重点对MTS/H₂体系化学气相沉积碳化硅进行了均相平衡计算,评价了体系中主要化合物对沉积碳化硅的作用. 结果表明,低温和高压下, SiCl₄和CH₄的含量最多, 不饱和物质和自由基的含量非常少, 温度的升高和压力的下降可显著提高不饱和物质和自由基的浓度; 高温和低压下, SiCl₂和C₂H₂可能是形成碳和硅的主要先驱体, 其它稳定物质如碳氢化合物、有机硅化合物和硅烷等由于浓度太小和表面反应粘结系数低, 对碳化硅的沉积可以不予考虑; 体系中几乎没有含Si--C和Si--Si键的物质, 说明碳化硅是经过碳和硅独立形成, 二者的相对速率决定了碳硅比.

Equilibrium Prediction of the Role of Key Species in the Chemical Vapor Deposition of Silicon Carbide

Based on Gibbs minimum free energy principle, homogeneous equilibrium calculations were focused by Factsage code for MTS/H₂ mixture. An assessment was made to determine the key species to SiC deposition. The results indicate that SiCl₂ and C₂H₂ may contribute to SiC deposition, and their formations are favored high temperature and low pressure. Most of silicon-containing and carbon-containing species are SiCl₄ and CH₄, at low temperature and high pressure. Other substances such as hydrocarbons, orgamosilicons and silane compounds are probably unimportant for deposition process because of their low concentrations and small surface reactive sticking coefficient. Silicon and carbon are formed independently, based on the fact that there are barely species containing Si--C and Si--Si in gas phase. The ratio of silicon and carbon in sample is determined by their kinetics, respectively.