高速沉积氮化硅薄膜对其化学键及性能的影响

Effect of High Deposition Rate on Chemical Bonds and Properties of SiN Film

采用等离子增强型化学气相沉积法(RF-PECVD),源气体为NH3/SiH4/N2的混合气体,在330℃的温度下沉积a-SiNx∶H薄膜。研究表明在反应气体流量一定的情况下,反应腔气压对薄膜沉积速率影响最大。采用Fourier红外吸收光谱技术分析a-SiNx∶H薄膜中化学键结构,随着沉积速率的提高,薄膜的化学键结构发生变化,N—H键含量和氮含量增大,Si—H键含量和氢含量降低。薄膜沉积速率是影响薄膜物理和光学性质的重要工艺参数。禁带宽度(E04)主要受薄膜中氮原子含量的调制,随着沉积速率增大,氮原子含量增大。另外,介电常数和折射系数则随之增大。最后得到满足薄膜晶体管性能要求的最佳工艺参数。

The hydrogenated amorphous silicon nitride （a-SiNx ：H） thin films were produced in a radio-frequency plasma-enhance chemical vapor deposition （rf-PECVD） system using NH3/SiH4/N2 mixture source gases at 330 ℃. It is found that the plasma power density plays main roles compared to the roles of the electrode spacing and chamber pressure on deposition rate. The structural properties of a-SiNx：H thin films are determined with Fourier Transform Infrared （FTIR） measurement and it is related to the deposition rate. The Si-H bond density decreases with increasing the deposition rate, while the N-H bond density increases. The deposition rate is an important parameter affecting the physical and optical properties. The band gap could be tuned by the N radical density which increases with increasing the deposition rate. The dielectric constant and refractive index decrease with increasing the deposition rate. Finally, process parameters are obtained for optimized performance of the thin film transistors.