氮化硅薄膜的热丝化学气相沉积法制备及微结构研究

Prepareation and Microstructure of Silicon Nitride Thin Films Deposited by Hot Wire Chemical Vapor Deposition Method

采用热丝化学气相沉积法,以SiH_4、NH_3、N_2为反应气源,通过改变氮气流量沉积氮化硅薄膜。通过紫外-可见(UV-VIS)光吸收谱、傅里叶红外透射光谱(FTIR)、X射线衍射谱(XRD)等测试手段对薄膜的光学带隙、键合特性及晶相进行表征与分析。结果表明:薄膜主要表现为Si-N键合结构,当N_2流量从20 sccm变化到40 sccm时,热丝能够充分的分解N_2,薄膜中N原子过量,其周围的Si和H能充分的与N结合。但由于N_2的解离能较高,当N_2流量高于40 sccm时,氮气在反应过程中对薄膜内的氮原子反而起到了稀释作用,薄膜的有序程度增大,光学带隙减小,致密性降低。当氮气流量达到150 sccm时,在2θ为69.5°处出现了晶化β-Si_3N_4的尖锐衍射峰,其择优取向沿(322)晶向,且Si_3N_4晶粒显著增大。因此,氮气流量对薄膜中的氮含量有显著影响,适当的增加氮气流量有利于制备出优质含有小晶粒β-Si_3N_4薄膜。

As keeping other deposition parameters constant,by changing the nitrogen flow rate,silicon nitride thin films were prepared by hot wire chemical vapor deposition method using SiH_4,NH_3,N_2 as reaction gas source. The optical band gap,crystalline phase,chemical bond types and other related information were characterized by fluorescence spectra（ PL）, ultraviolet-visible（ UV-VIS） light transmittance spectra,Fourier transform infrared transmissive optical absorption spectra（ FTIR）,X ray diffraction（ XRD） and other testing methods. The results showed that,the thin films are mainly composed of Si-N bond structure. When the nitrogen flow rates change from 20 sccm to 40 sccm,N_2 can be decomposed sufficiently by hot wire,nitrogen atom number in films are too much,and Si atom and H atom can combine fully with N atom. But,because nitrogen has the higher dissociation energy,when nitrogen flow rates are more than 40 sccm,excessive nitrogen in reaction process play a role of diluting the nitrogen atoms function in the films instead,and with increasing of the degree of order of the films,decreasing of the optical band gap and compactness. When the nitrogen flow rate reaches 150 sccm,thefilm has a sharp diffraction peak of the crystallization β-Si_3N_4 at 69. 5°（ 2θ）,and preferential growth orientation along（ 322） crystal orientation, with increasing of the silicon nitride crystal grains significantly. Therefore,nitrogen flow rates have a significant effect on nitrogen content in films,and the proper increasing of nitrogen flow rate is beneficial to preparation of high quality silicon nitride films containing β-Si_3N_4 small crystal grains.