臺灣博碩士論文加值系統

本研究以高頻電漿化學氣相沉積法(VHF-PECVD, 40.68MHz)針對微晶矽薄膜太陽能電池製程中，以四極柱質譜儀(Quadrupole Mass Spectroscopy, QMS)結合電漿放射光譜儀(Optical Emission Spectroscopy, OES)作為即時分析工具，探討改變操作參數(功率、壓力、氣體配比)對電漿性質及鍍膜速率與結晶率之影響，並進行電漿活性物種濃度之全定量分析。
實驗結果發現在微晶矽製程中提高電漿功率有助於提升解離率與鍍膜速率及膜材結晶率。在固定總流量提高SiH4配比時解離率雖然下降，但因為SiH4流量提高而總解離量提升而鍍膜速率升高，然而氫氣的減少卻導致結晶率下降。壓力增加時，電子平均自由徑下降，各物種解離量也隨之下降，但氫原子在電漿中濃度提高可增加對膜面的蝕刻效率使解離率增加。而在結合質譜儀與光譜儀分析結果發現，利用OES之H/SiH強度來估算微晶矽薄膜表面結晶度雖可得到相符合之趨勢，若是利用氫原子與SiHx物種之通量比值來計算其結晶率能更具有代表性。
本研究亦建立了微晶矽之電漿反應數學模型，包含monosilane與disilane相關的氣相及表面鍍膜反應。改變操作參數探討其對模型之影響發現，SiHx自由基物種濃度以SiH3最高、SiH2次之，Si2Hx自由基物種濃度則以Si2H5最高。利用電漿模型與實驗值比較電漿主要物種組成及解離率，發現在高解離率條件下兩者物種密度最為接近。以電漿模型進行鍍膜反應之動力學分析，發現電子之形成與消耗分別為與H2及H2+碰撞而反應為主，SiH4生成為SiH3與膜表面H反應為主，其消耗則與氫原子反應生成SiH3較多。另外在低功率時SiH4易解離成SiH3而貢獻於鍍膜，高功率下之鍍膜機制則以Si2H5物種占多數。

In this study, the plasma diagnostics tools (including actinometrics OES and QMS) were used to investigate the influences of operating parameters on intrinsic layer deposition process of μc-Si:H thin film solar cell in parallel-plate PECVD system with an excitation frequency of 40.68 MHz (VHF). The diagnostics results were correlated to deposition rate and crystalline fraction of deposited silicon films. A combination of experimental diagnostics and computational modeling was utilized to understand the main reaction mechanism in the plasma.
The plasma diagnostic results show that when plasma power is increased, both the silane dissociation efficiency and deposition rate are increased. Meanwhile, it also benefits to film’s crystallinity. Higher silane flow rate leads to a slightly decreased in silane dissociation efficiency, however there are much more dissociated radicals contributed to film growth. When operating pressure is increased, both the silane dissociation efficiency and deposition rate are decreased. Since higher pressure corresponds to higher species collision frequency, the H atoms get higher probability to etch silicon surface, resulting in better film’s crystallinity. By comparing OES and QMS results, quantitative analysis of the main species in the plasma can be achieved. On the basis of theoretical deposition model, we have proposed a flux ratio of H atom to SiHx radical as a new indicator of crystallinity during film growth of μc-Si:H.
Finally, a global model of SiH4/H2 plasma is developed. Both gas phase plasma chemistry and silicon film deposition process are included in the model. The model is found to capture the trend in experiment results on the effect of operating parameters on film deposition rate and active species concentrations in the plasma.

目錄
中文摘要 I
Abstract II
致謝 III
目錄 IV
表目錄 VI
圖目錄 VII
第一章 前言 1
1-1 研究動機 1
1-2 研究目的 2
第二章 文獻回顧 4
2-1 電漿簡介 4
2-2 高頻電漿源簡介 7
2-3 電漿診斷簡介及應用於微晶矽薄膜製程文獻整理 8
2-4 微晶矽薄膜成長機制文獻整理 13
第三章 研究方法與原理 17
3-1 實驗規劃與流程設計 17
3-1.1 實驗流程 17
3-1.2 實驗設備 19
3-2 儀器及原理 21
3-2.1 四極柱質譜儀 21
3-2.2 電漿放射光譜儀 25
3-2.3 薄膜表面輪廓量測儀 28
3-2.4 拉曼光譜儀 29
3-3 零維電漿模型 31
3-3.1 Ar/SiH4/H2電漿零維模型之建立 36
第四章 結果與討論 38
4-1 微晶矽質譜分析 38
4-1.1 質譜定性分析 38
4-1.2 改變電漿功率之微晶矽質譜分析 40
4-1.3 改變SiH4配比之微晶矽質譜分析 44
4-1.4 改變操作壓力之微晶矽質譜分析 45
4-2 微晶矽光譜分析 46
4-2.1 光譜定性分析 46
4-2.2 改變電漿功率之微晶矽光譜分析 48
4-2.3 改變SiH4配比之微晶矽光譜分析 51
4-2.4 改變操作壓力之微晶矽光譜分析 54
4-3 質譜結合光譜分析 57
4-3.1 通量比與結晶率分析 57
4-3.2 由半定量至定量分析 60
4-4 電漿模型分析 65
4-4.1 零維電漿模型 65
4-4.2 生成速率分析 72
第五章 結論 76
參考文獻 78
附錄 82

表目錄
Table 2-1 電漿診斷之文獻整理 12

Table 3-1 實驗反應器之型號、規格 19
Table 3-2 實驗氣體種類、純度及來源 19
Table 3-3 零維模型物種 36

Table 4-1 不同功率下腔體中SiHx(x≦3)之殘留比值 41
Table 4-2 不同功率下腔體中各處薄膜沉積情形 42
Table 4-3 不同SiH4配比下腔體中SiHx(x≦3)之殘留比值 44
Table 4-4 不同SiH4配比下腔體中各處薄膜沉積情形 44
Table 4-5 不同操作壓力下腔體中SiHx(x≦3)之殘留比值 45
Table 4-6 不同操作壓力下腔體中各處薄膜沉積情形 45
Table 4-7 SiH4/H2/Ar電漿放射光譜波峰位置及起始能量 47
Table 4-8 不同電漿功率下電漿中物種放射光譜強度 49
Table 4-9 不同SiH4配比下電漿中物種放射光譜強度 52
Table 4-10 不同操作壓力下電漿中物種放射光譜強度 55
Table 4-11 氫氣電漿反應莫耳數變化 60
Table 4-12 氫氣電漿反應分壓變化 60

圖目錄
Fig. 2-1 電漿各反應示意圖 6
Fig. 2-2 電漿當中物種與SiH4、H2 分子的二次反應 15
Fig. 2-3 穩定狀態下電漿活性物種密度 15
Fig. 2-4 微晶矽微結構變化 15
Fig. 2-5 微晶矽形成之(a)表面擴散(b)蝕刻(c)化學退火模型 16

Fig. 3-1 研究流程圖 18
Fig. 3-2 實驗設備示意圖 20
Fig. 3-3 實驗設備實體圖 20
Fig. 3-4 四極柱質譜儀實體圖及示意圖 21
Fig. 3-5 四極柱質量過濾器示意圖 23
Fig. 3-6 二次電子倍增管示意圖 23
Fig. 3-7 法拉第杯示意圖 24
Fig. 3-8 SiH4/H2之能階狀態圖 25
Fig. 3-9 放射光譜系統示意圖 27
Fig. 3-10 放射光譜系統實體圖 27
Fig. 3-11 α-step實體圖及示意圖 28
Fig. 3-12 拉曼光譜儀實體圖及示意圖 30
Fig. 3-13 零維模型中CSTR模式之電腦模擬求解流程 31

Fig. 4-1 電漿激發前後質譜關係圖 39
Fig. 4-2 Ar/SiH4/H2電漿之OES全譜圖 46
Fig. 4-3 不同電漿功率下物種之光譜強度圖 49
Fig. 4-4 改變功率之微晶矽薄膜拉曼散射光譜全譜圖 50
Fig. 4-5 結晶率隨電漿功率之變化 50
Fig. 4-6 不同SiH4配比下物種之光譜強度圖 52
Fig. 4-7 改變SiH4配比之微晶矽薄膜拉曼散射光譜全譜圖 53
Fig. 4-8 結晶率隨SiH4配比之變化 53
Fig. 4-9 不同操作壓力下物種之光譜強度圖 55
Fig. 4-10 改變操作壓力之微晶矽薄膜拉曼散射光譜全譜圖 56
Fig. 4-11 結晶率隨操作壓力之變化 56
Fig. 4-12 不同電漿條件下光譜SiH與質譜SiH4之關係 58
Fig. 4-13 改變電漿條件於矽薄膜之通量比、H/SiH與結晶率變化 59
Fig. 4-14 H2/Ar電漿中質譜與光譜相對關係 61
Fig. 4-15 改變電漿條件，H、SiH4、SiH3及Si2H6之濃度變化 64
Fig. 4-16 不同電漿條件下模型預測之電子密度與電子溫度 67
Fig. 4-17 不同電漿條件下模型預測之物種濃度 68
Fig. 4-18 不同電漿條件下實驗與模型預測之物種濃度 70
Fig. 4-19 不同電漿條件下實驗與模型預測之SiH4解離率 71
Fig. 4-20 電漿中關於電子之重要反應式 73
Fig. 4-21 電漿中關於SiH4之重要反應式 73
Fig. 4-22 電漿中關於SiH3之重要反應式 74
Fig. 4-23 電漿中關於H之重要反應式 74
Fig. 4-24 電漿中關於鍍膜之重要反應式 75
Fig. 4-25 電漿中關於Si2H6之重要反應式 75

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