高频等离子体化学气相沉积法制氮化硅的化学平衡计算

CHEMICAL EQUILIBRIUM COMPUTATION FOR PREPARATION OF Si 3N 4 BY RADIO FREQUENCY PLASMA CHEMICAL VAPOR DEPOSITION METHOD

基于Ｇｉｂｂｓ自由能最小原理，开发了热力学通用程序，分析了以Ａｒ为载气、ＳｉＣｌ４和ＮＨ３为原料、在高频等离子体化学气相沉积反应器中制备Ｓｉ３Ｎ４超细粉的化学热力学过程得到了在典型条件下系统的主要组成，分析了温度、反应物浓度对平衡组成的影响通过热力学模拟，发现当ＳｉＣｌ４进料口在前，ＮＨ３进料口在后，且两个进料口均在高频等离子体尾焰处时，经脱ＮＨ４Ｃｌ的产物中氮含量较高。

A general purpose computer program was developed based on the minimization of Gibbs free energy of a chemical system and used to analyze the multi component system for synthesizing ultrafine Si 3N 4 powder The influence of temperature,concentration of NH 3, H 2,N 2,H 2O,O 2 on component concentration was investigated It is found by numerical simulation that the inlet position of SiCl 4 should be higher than that of NH 3,and they should be located at the hind part of the plasma torch if the effect of torch temperature is considered The best molar ratio of NH 3 to SiCl 4 should be (6～8):1 The raw materials should be as pure as possible Thus,the highest nitride content could be obtained N 2 or H 2 can be used to replace some or even all the Ar to improve the yield of Si 3N 4 and reduce the cost The simulated results were verified by experimental investigation