射频功率对RF-PECVD法制备纳米硅薄膜结构特征和光学特性的影响

Effect of RF powers on microstructural characteristics and optical properties of nc-Si∶H thin films by RF-PECVD

利用射频等离子体增强型化学气相沉积(RF-PECVD)工艺,以SiH4和H2作为反应气体源,在石英衬底上制备了氢化纳米硅(nc-Si∶H)薄膜。其中衬底温度为250℃,H2稀释比为99%,反应压强为133Pa和射频功率为20～60W。采用α-台阶仪、X射线衍射仪(XRD)、Raman光谱仪、傅立叶变换红外光谱仪(FT-IR)和紫外-可见光分光光度计等对薄膜的结构特征和光学特性进行了测试研究。结果表明,随着射频功率的增大,nc-Si∶H薄膜的沉积速率增加,晶化率提高,晶粒尺寸增大和氢含量减小,同时薄膜的吸收系数增强,光学带隙变窄,结构有序性增强和带尾态宽度减小。

The hydrogenated nanocrystalline silicon （nc-Si · H） films were fabricated on quartz substrates by radio frequency plasma enhanced chemical vapor deposition （RF-PECVD） method with the substrate temperature of 250℃, H2 dilution ratio of 99%, the reaction pressure of 133Pa and RF power of 20-60W, using Sill4 and H2 as the gas source. The microstructures and optical properties of thin films were studied by alpha-step instru- ment, X-ray diffraction （XRD）, Raman spectroscopy, Fourier transform infrared spectroscopy （FT-IR） and UV-Vis spectrophotometer. The results show that, with the increasing of RF power, the nc-Si ： H deposition rate increased, the crystallization rate and grain size also increased, and the hydrogen content would decrease. Simultaneously, the absorption coefficient of the films was enhanced, the optical band gap became narrow, the structural order was enhanced and the width of the band tail would decrease.