用于微测辐射热计氮化硅薄膜特性与结构研究

Study on Characteristics and Structures of Amorphous Silicon Nitride Thin Films Applied in Micro-Bolometer

氮化硅(SiNx∶H)薄膜通常用作微测辐射热计焦平面阵列的支撑层、绝缘或隔热层。通过射频等离子体增强化学气相沉积(PECVD)制备了富硅型(0.80≤x≤1.16)氮化硅薄膜,利用X射线光电子能谱(XPS)和傅里叶红外透射光谱(FTIR)分析了薄膜的微观结构。发现薄膜内部保存了Si3N4基本结构单元,除此之外,波数位于790,820和950 cm-1的Si-N键的伸缩振动峰分别对应为Si3-Si-N,N2-Si-H2,及H-Si-N3结构单元;运用曲率方法测量了不同硅烷(SiH4)流量条件下制备的氮化硅薄膜样品的残余应力,发现薄膜应力一般表现为张应力,但随着硅烷流量的增大,薄膜的张应力减小。理论分析发现,H-Si-N3结构单元使薄膜呈现张应力,而Si3-Si-N结构单元以及Si-Si键相对地表现为压应力。因此,通过优化制备工艺,获取理想的薄膜微观结构,能更理性地调控薄膜的残余应力。

Silicon nitride films are widely used in micro-bolometer focal plane arrays as supporting layer and insulation layer.In this paper,silicon-rich hydrogenated amorphous silicon nitrides（α-SiNx∶H,0.80≤x≤1.16） were prepared by radio-frequency plasma-enhanced vapor deposition.The film microstructures were analyzed using X-ray photoelectron spectroscopy（XPS） and Fourier transimission infrared spectroscopy（FTIR）.Results reveal that α-SiNx∶H contain the basic structural units of Si3N4.Moreover,the Si-N stretching modes located at 790,820 and 950 cm-1,are ascribed to Si3-Si-N,N2-Si-H2,and H-Si-N3 configurations,respectively.The residual stresses were measured by curvature measurement,indicating that the residual stress in the film generally exhibits tension,but this tensile stress gradually decreases while the SiH4 flow rate increases.The theoretical analysis shows that the H-Si-N3 configuration is helpful for developing tensile stress,while the Si3-Si-N and Si-Si configurations are helpful for compressive stress.Therefore,by optimizing the processing conditions,α-SiNx∶H,with suitable microstructures can be prepared,by which the film stress can be better controlled.