臺灣博碩士論文加值系統

隨著矽晶太陽能產業的發展，提升效率的同時業界也要求降低成本，其中提高太陽能發電效率來以及晶圓薄化都是有效降低成本的方法，但是在矽晶圓薄化的過程中表面比率隨之增加，因此必須應用更好的表面鈍化層來降低表面載子再復合的機率，Al2O3是一種高介電材料的介電層，並且擁有足夠的固定電荷產生電場，利用場效的方式阻止少數載子在表面再復合的機率，能夠大大提升表面鈍化的效果，同時Atomic Layer Deposition俗稱ALD的鍍膜技術是近年來發展快速的一個薄膜製成的方法，能夠利用cycle數精準的控制膜厚，並擁有良好的均勻性與極高高寬比的特性使得現今很多企業應用在薄膜製程上。
本實驗在n型矽基板上利用ALD鍍製Al2O3薄膜，研究不同厚度、不同退火條件、SiNx的有無對於有效載子生命週期的影響，並將試片鍍覆鋁電極製作成金屬-氧化物-半導體的MOS結構，透過高頻電容-電壓曲線量測的結果數據中，計算矽基板的摻雜濃度、空乏區寬度、平帶電壓以及氧化層固定電荷，並且利用氧化層固定電荷與有效載子生命週期進行比照，說明ALD Al2O3的場效效果對於有效載子生命週的影響。
研究結果顯示退火處理及PECVD中的高溫製成會使氧化層的固定電荷由正轉成負電，此時場效鈍化的效果明顯提高這也反映在PCD量測的有效載子生命週期上的結果，並且對於覆蓋上SiNx的試片有無退火的處理，氧化層固定電荷變化與有效載子生命週期的趨勢相符，此外在鍍膜的過程中利用OM觀察薄膜表面也發現隨著薄膜厚度的提高與熱處理次數blister出現的密度也隨之增加，但是對於有效載子生命週期的結果並無直接的影響。

The surface to volume ratio is increasing due to the cost-driven reduction of the solar cell thickness thickness, which makes surface passivation a decisive factor for the final solar cell efficiency. Al2O3 have a high dielectric constant as a dielectric layer and have sufficient build-in nagative fixed oxide charge which generates an electric field. This field effect prevent the chances of minority carrier recombine at the surface which can greatly enhance the surface passivation.
Meanwhile Atomic Layer Deposition (ALD) coating technology is developing rapidly in recent years, a film thickness can precisely control by number of cycles. Its good uniformity characteristics and an excellent aspect ratio so that today many companies used in the film manufacturing process.
In this study, different thickness of ALD Al2O3 under different annealing conditions and PECVD SiNx are plated on n type Si wafers to examine the passivation effect. After that the samples are made into MOS structure to get the high-frequency capacitance-voltage data. The calculation of the doping concentration of the silicon substrate, the depletion zone width, the flat band voltage and fixed oxide charge will be found.
The results show that annealing treatment and high temperature PECVD lead Al2O3 fixed oxide charge change from positive into negative, then the field effect passivation has improved significantly which is also reflected in the PCD effective carrier lifetime measurement of results and for covering the SiNx. The trend of lifetime and fixed oxide charge density versus different thickness of ALD Al2O3 are the same. This explains the good passivation effect is due to more fixed oxide charge in oxide layer. In addition, we observe that there are blisters generated at film surface. With increasing film thickness and number of heat treatment density blister appeared also increases but no direct effect on the effective carrier lifetime results.

第1章 前言與研究動機 1
1.1研究背景 1
1.1.1 太陽能電池的發展 1
1.1.2 太陽能電池面臨的挑戰 3
1.1.3 降低表面再復合速率 4
第2章 文獻回顧 5
2.1載子再復合機制[5, 6] 5
2.1.2 Surface Passivation 6
2.1.2良好的表面鈍化機制 7
2.1.3 Al2O3 表面鈍化的效果 7
2.2 Atomic Layer Deposition 9
2.3 Blister phenomenon 10
2.3.1 Blister 的特性 10
2.3.2 Blister 在Al2O3中對passivation的影響 12
2.3.3 Blister在Al2O3中對熱穩定性的影響 14
2.4金氧半(MOS)數據分析 16
2.4.1金氧半(MOS)結構理論 16
2.4.2 MOS結構裡的電荷 19
2.4.3 MOS結構中的電容 22
2.4.5 MOS電容修正 23
第3章 實驗方法及流程 26
3.1 MOS製備 26
3.1.1基板前處理 27
3.1.2 ALD氧化層製備 27
3.1.3退火處理 28
3.1.4 PECVD SiNx製備 29
3.1.5電極的鍍製 30
3.2 lifetime量測 31
3.3 MOS元件電性量測 34
3.3.1高頻電容-電壓曲線量測 34
第4章 實驗結果與討論 35
4.1.1 有效載子生週期結果 35
4.1.2表面再復合速率與開路電壓關係 36
4.2 元件品質的修正 36
4.3 MOS 電容-電壓曲線分析 38
4.3.1 MOS電容-電壓值結果 38
4.3.2空乏區寬度 41
4.3.3矽基板摻雜濃度 41
4.3.4平坦能帶電壓 42
4.3.5氧化層固定電荷 43
4.3.6氧化層固定電荷對表面再復合速率的影響 45
4.4 實驗參數對Blister的影響 46
第5章 結論 49
參考文獻 50

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