矽基薄膜與光伏元件電漿輔助化學氣相沉積製程研究-實驗探討與電漿模擬分析

Plasma Enhanced Chemical Vapor Deposition of Silicon Based Thin Films for Photovoltaic Application – Experimental study and Simulation Analysis

林鴻彬

指導教授 ： 柳克強

國立清華大學/原子科學院/工程與系統科學系/碩士(2014年)

摘要

本研究旨在探討矽基薄膜電漿化學氣相沉積製程中電漿特性對薄膜特性之影響，內容包含實驗與模擬兩部份，前者是對非晶矽鍺薄膜製程，利用OES (Optical Emission Spectroscopy)分析特徵譜線之變化和非晶矽鍺薄膜特性之關係，後者則是對於應用於HIT太陽電池之非晶矽薄膜製程，以流體模型模擬製程電漿，探討功率、壓力和矽烷氣體流量對於電漿特性、矽烷耗盡率和高階矽烷分子生成量之影響。實驗結果顯示，OES-ratio(Si/Ge)與薄膜能隙和光敏性皆呈現相同的變化趨勢，代表OES-ratio(Si/Ge)與薄膜中矽鍺比例具強烈關聯性。而OES-ratio(Si/SiH)和OES-ratio(Hβ/Hα)可以定性分析電漿中的電子溫度，在改變功率與矽烷流量的情況下，兩種ratio呈現不規則的變化，若是增加腔體壓力與鍺烷流量OES-ratio(Si/SiH)和OES-ratio(Hβ/Hα)皆有下降的趨勢，最後是利用H2放射強度來分析電漿中的電子密度，在改變壓力的情況下，H2放射強度無固定趨勢可循，而在其他的情況下，如H2放射強度會隨著功率上升，表示電漿中的電子密度隨之上升，另外是改變氣體流量的情況，當氣體流量上升時，電子密度有下降的趨勢。在製程過程中，利用OES分析可以得知在不同參數下薄膜能隙的改變以及電漿特性的變化。
另一方面模擬結果顯示，當功率上升時，由於SiH2粒子通量密度劇烈地上升，所以矽烷耗盡率與高階矽烷粒子通量密度比皆有上升的變化趨勢。而在改變壓力與矽烷氣體流量的情況下，矽烷耗盡率與高階矽烷粒子通量密度比有著相反的變化趨勢。

關鍵字

電漿輔助化學氣相沉積 ； 電漿模擬

並列摘要

The purpose of this study is to investigate the influence of the plasma property on the thin film property in plasma enhanced chemical vapor deposition (PECVD) processes which are employed for deposition of silicon based thin film. This study includes both experimental and simulation analysis. Experimentally, optical emission spectroscopy was employed for analysis in PECVD plasma discharge for a-SiGe:H films. Correlations between the variation of the intensities of the characteristic emissions of the gaseous species important for the film deposition and properties. On the other hand, numerical simulation using fluid model was also conducted for analysis of capacitively-coupled SiH4/H2 plasma discharges operated at very high frequencies (VHF) for deposition of a-Si:H film which was used in the HIT solar cells. In simulation study, the effect of silane depletion and higher silane species under different process parameter (power, pressure and silane flow rate). Experiment shows OES-ratio Si/Ge shows the same trend with film bandgap and photosensitivity. It means OES-ratio Si/Ge exists strong correlations to the silicon/germanium content in the film. Besides, OES-ratio Si/SiH and OES-ratio Hβ/Hα can be used to analysis electron temperature in the plasma. But these two OES ratio show the abnormal variation as power/silane flow rate are varied. However, when pressure and germane flow rate increases, then OES-ratio Si/SiH and OES-ratio Hβ/Hα will descend. Finally, H2 emission intensity can be used to analysis electron density of plasma. H2 emission intensity doesn’t have trend to follow as pressure is varied. But in the others process condition, H2 emission intensity increases with power, it means higher electron density in the plasma. On the other hand, electron density descend when the total gas flow rate increases. So OES analysis method can be used to know the variation of film bandgap and plasma property under different process parameter.
In simulation studies, silane depletion and higher silane species flux ratio increase with power due to SiH2 number density increase acutely. In addition, silane depletion and higher silane species flux ratio have a opposite trend as pressure/silane flow rate are varied.

並列關鍵字

PECVD ； silicon based thin films

參考文獻

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