氮化矽薄膜色差均勻性對太陽能電池片效能之研究

Abstract

本論文乃研究多晶矽太陽能電池( Poly-crystalline silicon solar cells )抗反射層薄膜( Antireflection thin films)製程之技術，而抗反射SiNx薄膜已經成為單晶或多晶矽薄膜太陽能電池製程關鍵步驟之ㄧ。目前業界皆以電漿輔助化學氣相沉積法(Plasma Enhanced Chemical Vapor Deposition, 簡稱PECVD)法來進行沉積SiNx薄膜。然而，從終端的應用產品上可發現到，實際太陽能電池片上呈現出差異性的抗反射層薄膜沉積顏色，造成太陽能電池模組外觀上突兀與不協調。在經由研究證實發現，此顏色差異源自於抗反射層薄膜厚度不同所表現。此外，抗反射薄膜厚度不均勻，會在介面處影響金屬燒結階段穿透程度與矽合金形成的可能性變化，而導致太陽能電池片上，並聯電阻與串聯電阻的電性變化，間接影響電池片光電轉換效益表現。 研究中針對PECVD進行沉積SiNx薄膜過程中調整反應壓力、氣體流量變化、反應射頻、氣體比例變化、製程溫度對其抗反射薄膜生成的影響。根據實驗結果和參考文獻報導可歸納出(1) 氣體流量與反應壓力變異會明顯影響薄膜沉積生長率；(2) 反應射頻變異同樣明顯對增加薄膜沉積速率，但卻導致結構鬆散；(3) 氣體流量比例SiNx薄膜反射率；(4) 反應温度方面則影響表面原子活性與遷移率，提升薄膜緻密性。這些製程參數條件對於進行沉積薄膜均勻性並沒有絕對的關聯性。 因此針對薄膜沉積顏色異常特徵性，特別進行載具設計實驗觀察其對其沉積薄膜特性與光學特性的影響。最終實驗結果發現變更載具與晶片接觸設計，可確實顯著改善晶片太陽能電池片上抗反射層薄膜厚度均勻性，意即能減少外觀上晶片顏色色差，同時可兼顧反射率與光電轉換效率。

The research aims to study the fabrication of antireflection thin films for poly-crystalline silicon solar cells. The antireflection SiNx thin films have already treated as the turnkey process for silicon solar cells. Plasma-enhanced chemical vapor deposition (PECVD) technique on SiNx films is widely used in PV industry. Actually, the solar cells exhibit different colors in the thin films, which have led to unexpected and uncoordinated exterior. The causes of these variances in the films deposition colors, through this research, have been found to be the incongruity in thickness of the antireflection films. Otherwise, such disproportionate thicknesses have caused possible distortion in the contact formation and the formation of silicon alloy at its interfaces. Such disproportionate of antireflection thin films will impact metal penetration rate and silicon alloy in the interface. Hence, the arising of series and parallel resistance in the PV transforming performance deteriorates the cell efficiency. In this thesis, various deposition parameters are performed by turning the process parameters (pressure, gas flows, MW plasma power, gas flow ratio and substrate temperature) of PECVD. We find that (1) the gas flow and the reaction pressure variations can significantly affect the growth rate; (2) the reaction of the RF variability was also significantly increase the film deposition rate, but it led to a loose structure; (3) gas flow ratio determines the reflective index; (4) the reaction temperature affect the activity of substrate surface atoms, and enhance film densification. In addition, the new carrier design can achieve improvement in layer uniformity and a slight color difference. This approach maintains refraction index and optoelectronic transforming performance.