利用軟、硬X光以多角度解析半導體界面薄膜

Investigation of the Semiconductor Interfacial Thin Film Using The AR-XPS Technique Combing with Soft and Hard X-rays

近年來，太陽能電池的發展由於國家發電配比大幅增加綠電比例而備受關注，因此太陽能電池光電轉換效率成熱門話題，而太陽能電池界面上的電子、電洞分流品質，是影響其光電轉換效率的關鍵之一。然而矽晶於生成時產生的缺陷，會提高載子於pn界面上復合機率，導致其光電轉換效率下降。研究顯示高品質表面鈍化層能有效提升太陽能電池光電轉換效率，因此如何製造出高品質表面鈍化層成為重要課題。在眾多鈍化層材料中，氧化鋁（Al2O3）薄膜能促進更長的載流子壽命，降低鈍化光電元件的本質缺陷，為良好鈍化層及蝕刻阻擋層，同時被廣泛應用於太陽能與半導體產業中。本研究利用非真空原子層沉積設備（Atmospheric Pressure Atomic Layer Deposition, APALD）於單晶矽上沉積Al2O3薄膜，沉積Al2O3過程中在Al2O3與矽晶圓界面間會自然生長出氧化矽（SiOx）薄膜，此SiOx厚度與品質將影響太陽能電池元件光電轉換效率。為觀察SiOx厚度與退火溫度之間關係，本實驗結合軟、硬X光光電子能譜儀以角度解析X光光電子能譜技術（Angle-Resolved XPS, AR-XPS）於不同角度觀察SiOx薄膜厚度隨退火溫度的變化，以及薄膜界面的組成與元素價態分佈，此外，本實驗更進一步整合各角度所得之資訊，經由軟體計算獲得非破壞式元素縱深分佈資訊，從縱深分佈分析結果顯示SiOx薄膜厚度將隨退火溫度增加而增厚。

In recent years, the power conversion efficiency (PCE) of the silicon-based solar cells has attracted wide attention. The recombination quality of electron and hole at the interface plays an important role to the PCE of the photovoltaics. However, defects generated during the formation of silicon crystals could increase the probability of the recombination of carriers at the p-n junction interface, leading to a decreased efficiency in PCE. Studies have shown that high-quality passivation layers on the surface could effectively improve the PCE of the photovoltaics. Thus, the manufacture of the high-quality passivation layers on the surface has become an important topic. Aluminum oxide (Al2O3) thin films are widely used in the solar cells and semiconductor industries as excellent passivation layers, etching stop layers because it prolongs the carriers lifetimes and decreases the intrinsic defects of photovoltaic devices. In this study, the atmospheric pressure atomic layer deposition (APALD) technique is used to grow Al2O3 thin film on single-crystal silicon with different annealing process. A native SiOx thin films between Al2O3 and single crystal silicon was formed. The thickness and quality of the SiOx thin film play an important role for the highly efficient PCE of solar cells. To observe the relationship between SiOx thickness and annealing temperatures, angle-resolved X-ray photoelectron spectroscopy (AR-XPS) combining with soft and hard X-rays was used to examine the SiOx thin films with different take-off angles. In addition, the thickness information of the SiOx thin film can be obtained by integrating the information obtained from each angle and calculating through software. The results indicated that the thickness of the SiOx thin film increased with the increasing annealing temperatures.