晶体硅微粉气相氮化及氮氧化条件

Conditions for Gaseous Nitridation and Oxynitridation of Crystalline Silicon Powders

氮化硅及氮氧化硅粉体在多晶硅光伏产业中有重要应用。本文研究其气相反应形成条件。研究结果显示,晶体硅微粉的气相氮化及氮氧化特性与体材大不相同,它使得硅的氮化和氮氧化得以在体系中氧分压远高于热力学临界平衡氧分压、处于氧化硅稳定区的条件下实现。其原因在于反应过程中粉体表层氧化反应后耗氧,使粉体内部实际氧分压大幅度降低。实验结果表明,晶体硅微粉的气相氮化约需1400℃方能有效进行,在气相反应条件下,α-Si3N4与β-Si3N4均能形成,随保温时间延长,α-Si3N4相对量提高;晶体硅微粉在氮-氧混合气体中的氮氧化行为对气氛的氧分压十分敏感,氧分压较高时形成SiO2并阻止反应进一步进行,较低时形成Si3N4,氧分压为0.1atm时较适合Si2N2O形成。

Powders of silicon nitride and silicon oxynitride are important materials to poly-crystalline based photovoltaic industry.A study of their formation conditions in gaseous reactions has been carried out.The results show that the reaction process of silicon powders is greatly different from that of bulk silicon.With silicon powders,silicon nitride and silicon oxynitride can be formed under much higher oxygen partial pressure than the critical oxygen partial pressure decided by thermodynamic equilibrium.The reason is that oxygen is exhausted in the reaction with surface layer of powders,so that actual oxygen partial pressure for the particles underneath becomes much lower.The experiments show that heating to a temperature as high as 1400℃ is required for an effective gaseous nitridation.Behavior of the silicon oxynitridation in mixed nitrogen-oxygen is very sensitive to the oxygen partial pressure,oxidation occurring at higher oxygen partial pressure,and nitridation occurring at lower oxygen partial pressure.Under the present experimental conditions used,0.1atm of oxygen partial pressure was appropriate for formating silicon oxynitride.