化学气相沉积中影蔽效应对硅薄膜表面形貌和微结构的影响

摘要

采用斜入射热丝化学气相沉积技术(OAD-HWCVD)，研究了气流入射角度(θ)对氢化非晶硅(a-Si：H)薄膜表面和微结构的影响。实验发现，薄膜厚度为1µm时，均方根粗糙度与tanθ成指数关系；在入射角度为75◦时，薄膜表面由自仿射表面转变为mound表面。采用拉曼谱和红外谱表征了硅薄膜的微结构随气流入射角度的变化。在薄膜转变为mound表面生长之前，随入射角度的增加，准局域的影蔽效应使得薄膜中微空洞的数目及尺寸增加，导致薄膜微结构因子升高、致密度下降、薄膜质量变差。在薄膜转变为mound表面生长之后，非局域的影蔽效应导致大尺度的空洞，同时薄膜中以Si-Hn(n>2)形式存在的氢增多。本文以非晶硅薄膜为例，结合标度理论，分析了薄膜生长过程中的表面形貌和微结构与影蔽效应的关系。%Influences of gas incident angle (θ) on surface morphology and microstructure of hydrogenated amorphous silicon (a-Si:H) thin films are investigated, which were grown using an oblique angle hot wire chemical vapor deposition (OAD-HWCVD) technique. An exponential relationship between the tanθ and RMS roughness is observed. The film surface morphology transforms from a self-affine surface into a mounded surface when the incident angle is larger than a critical angle θc(60◦ < θc < 75◦). Influences of θ on the microstructural properties of silicon thin films are characterized using Raman scattering and FT-IR measurements. As θ < θc, owing to the qusai-local shadowing effect, increasingθ increases the quantity and size of micro-voids, leading to the decrease of film density and quality. For θ > θc, the nonlocal shadowing effect causes the formation of large voids or cracks and the proportion of multi-hydride (SiHn, n>2) increases. Combined with the scaling theory, the relationship between the shadowing effect and the surface morphologies and microstructures of amorphous silicon thin films is discussed.