Evolution of infrared spectra and optical emission spectra in hydrogenated silicon thin films prepared by VHF-PECVD

• Published in: Chinese physics B Vol. 20; no. 7; pp. 440 - 445
• Main Author: 侯国付 耿新华 张晓丹 孙建 张建军 赵颖
• Format: Journal Article
• Language: English
• Published: 01.07.2011
• Subjects: Deposition; Emission spectra; Evolution; Infrared spectra; Peak frequency; PECVD法; Silanes; Silicon films; Thin films; VHF; 傅里叶变换红外光谱; 发射光谱仪; 氢化; 演变; 硅薄膜; 等离子体增强化学气相沉积
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/20/7/077802

A series of hydrogenated silicon thin films with varying silane concentrations have been deposited by using very high frequency plasma enhanced chemical vapor deposition （VHF-PECVD） method. The deposition process and the silicon thin films are studied by using optical emission spectroscopy （OES） and Fourier transfer infrared （FTIR） spectroscopy, respectively. The results show that when the silane concentration changes from 10% to 1%, the peak frequency of the Si-H stretching mode shifts from 2000 cm-1 to 2100 cm-1, while the peak frequency of the Si-H wagging-rocking mode shifts from 650 cm-1 to 620 cm-1. At the same time the SiH^＊/Ha intensity ratio in the plasma decreases gradually. The evolution of the infrared spectra and the optical emission spectra demonstrates a morphological phase transition from amorphous silicon （a-Si：H） to microcrystalline silicon （μc-Si：H）. The structural evolution and the p-c-SiH formation have been analyzed based on the variation of Ha and SiH^＊ intensities in the plasma. The role of oxygen impurity during the plasma process and in the silicon films is also discussed in this study.