添加H_2对SiH_4/N_2/Ar等离子体淀积的氮化硅电学和光学特性的影响

Effect of Hydrogen Addition on the Optical and Electronic Properties of Silicon Nitride Deposited by SiH_4/N_2/Ar Plasma

研究了加H2对SiH4/N2/Ar高密度、低离子能量的等离子体淀积的氮化硅薄膜(淀积的衬底温度为400℃)电学和光学性能的影响。实验结果表明,加入H2使氮化硅薄膜的光学带隙增加,其折射率以及在氢氟酸缓冲液中腐蚀速率减小,而XPS测试的N、Si原子比没有改变,均为1.3。FTIR测量表明,样品中Si-H键的密度低于仪器检测限,而添加H2的样品中N-H键密度稍增加。此外,由淀积的氮化硅膜构成的MIS结构的高频C-V测试(1 MHz)显示,当氢气流量从零增加到8sccm时,高频C-V的回滞幅度从(0.40±0.05)V降低到(0.10±0.01)V。基于这些实验结果和理论分析,表明了加适量H2能够促进弱的Si-Si键以及Si和N的悬挂键向Si-N键转化。

Influence of hydrogen addition on the optical and electrical properties of silicon nitride deposited at substrate temperature 400 ℃ by high-density and low ion energy plasma SiH4/N2/Ar has been investigated.The experimental results showed that the hydrogen addition caused an increment in optical gap of the silicon nitride film.In other hands,its refractive index and etching rate in buffered HF solution at 25 ℃ decrease with increment of hydrogen flow rate,where N/Si atom ratio of all samples measured by XPS is 1.3.FTIR observation further showed that Si-H bond density is below the detection limit and N-H bond density increases slightly in the film deposited by hydrogen addition.In addition,the hysteresis of high-frequency （1 MHz） C-V characteristics of MIS device which is composed of the silicon nitride as insulator layer decreases from （0.40±0.05） V to （0.10±0.01） V with increasing hydrogen gas flow rate from zero to 8 sccm.Based on these experimental results and theoretical analysis,it is deduced that the hydrogen addition seems to have capability of promoting the conversion of weak Si-Si bonds,Si and N dangle bonds to SiN bonds.