靶材及製程對太陽能電池鉬背電極薄膜特性的影響

Effects of Sputtering Targets and Processes upon Characteristics of Molybdenum Back Electrodes in Solar Cells

劉劍鋒(Chien-fong Liu)

指導教授 ： 王錫福

國立臺北科技大學/工程學院/材料及資源工程系研究所/碩士(2012年)

摘要

背電極是太陽能電池中影響吸收層的關鍵因素，需要有好的附著性、低片電阻、及高的光反射率以提高太陽能電池的效率。由於鉬金屬薄膜擁有良好的光反射率、電阻率低、對製程溫度相對穩定、與CIGS薄膜間有良好的歐姆接觸特性，因此常被選為CIS 及CIGS太陽能電池的背電極。
由於鉬的薄膜特性受到濺鍍製程參數影響，因此本研究針對鉬金屬靶材的濺鍍製程及薄膜特性最佳化進行研究，以外購之商用鉬靶材，在基板不加熱的狀態下，比較DC與RF兩種不同的濺鍍方式對薄膜特性的影響。其中，以DC濺鍍鉬背電極薄膜之最佳製程參數為：氬氣流量30 sccm，第一層濺鍍功率30 W、工作壓力12 mTorr、濺鍍10 min；接著第二層濺鍍功率50 W、工作壓力4.5 mTorr、濺鍍15 min，所生成的薄膜附著性均通過Scotch 膠帶測試 (tape test)，而其電阻率與反射率亦為最佳。RF濺鍍的最佳濺鍍參數則為：濺鍍功率100 W、氬氣流量30 sccm、第一層工作壓力12 mTorr、濺鍍5分鐘，接著再以工作壓力2 mTorr，濺鍍20分鐘鍍製第二層，可以獲得比DC濺鍍製程更佳的電阻率與反射率。

關鍵字

銅銦鎵硒太陽能電池 ； 金屬背電極 ； 直流式濺鍍 ； 射頻濺鍍

並列摘要

Back electrode in solar cells requires good adhesion with the absorption layer, low sheet resistance, and high reflectivity to improve the cell efficiency. Molybdenum metal thin film is often selected as the back electrode in CIS and CIGS solar cells due to its good reflectivity, low resistivity, stable process temperature, and good ohmic contact with the CIGS film.
In this study, the optimized sputtering process parameters of molybdenum metal targets and film characteristics are investigated. Sputtering processes by both direct current (DC) and radio frequency (RF) powers are tested. The optimal DC sputtering parameters of molybdenum back electrode are 30 sccm of argon flow, 30W of sputtering power, 12 mTorr of working pressure, followed by the second layer sputtered using 50 W power, 4.5 mTorr working pressure, and sputtering for 15 min. Such double layer thin film passes the Scotch tape test successfully and bear the low resistivity and high reflectivity. For RF sputtering, the optimized sputtering parameters are 100 W of sputtering power, 30 sccm of argon flow, 12 mTorr of working pressure, and 5 min of sputtering time for the first layer. The second layer is then using 2 mTorr working pressure and sputtering for 20 minutes to obtain the optimized resistivity and reflectivity. It is observed that the RF process deposited films demonstrates better properties than DC sputtering.

並列關鍵字

CIGS solar cells ； metal back electrode ； DC sputtering ； RF sputtering

參考文獻

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