电极间距对μc-Si_(1-x)Ge_x:H薄膜结构特性的影响

Influences of electrode separation on structural properties of μc-Si_(1-x)Ge_x:H thin films

采用射频等离子体增强化学气相沉积(RF-PECVD)技术,使用SiH4加GeH4的反应气源组合生长微晶硅锗(μc-Si1-x Gex:H)薄膜.研究了电极间距对μc-Si1-x Gex:H薄膜结构特性的影响.发现薄膜中的Ge含量随电极间距的降低逐渐增加.当电极间距降至7 mm时,μc-Si1-x Gex:H薄膜具有较大的晶粒尺寸并呈现较强的(220)择优取向,同时具有较低的微结构因子.通过薄膜结构特性的变化分析了反应气源的分解状态,认为Ge含量的提高主要是SiH4的分解率降低所导致的.在较窄的电极间距(7 mm)下,等离子体中GeH3基团的比例较大,增强了Ge前驱物的扩散能力,使μc-Si1-x Gex:H薄膜的质量得到提高.

Hydrogenated microcrystalline silicon germanium （μc-Sil-xGex：H） thin films have been prepared by radio frequency plasma-enhanced chemical vapor deposition （RF-PECVD） using a mixture of Sill4 and GeH4 as the reactive gases. Effects of electrode seParation on the structural properties of μc-Sil-xGex：H thin films have been investigated. Results show that reduction of the electrode separation can increase the Ge content in the films. Moreover, μc-Sil-xGex：H thin film deposited at a lower electrode separation of 7 mm possesses not only a stronger （220） orientation and a larger grain size, but also a lower microstructural factor. Then, the decomposition characteristics of the reactive gases are analyzed according to the variation of the structural properties of the μc-Sil-xGex：H thin films. It is found that the increase of the Ge content is due to the decrease of the Sill4 decomposition rate in the plasma. While the better film quality obtained at the lower electrode separation is attributed to the enhancement of the diffusibility of the Ge precursors caused by improving the proportion of GeH3 radicals