博碩士論文 983203052 詳細資訊


姓名 温琬婷(Wan-ting Wun)  查詢紙本館藏   畢業系所 機械工程學系
論文名稱 柴氏法生長單晶矽過程之氧雜質傳輸控制數值分析
(Numerical simulation of the oxygen transport of the CZ silicon crystal growth process)
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摘要(中) 單晶矽是太陽能電池的主要原料之一,而氧在柴氏法生長單晶矽中是個重要的雜質,會影響太陽能電池效率。常見的降氧方法有成三種:(1)降低石英坩堝壁溫度以減少坩堝釋氧量、(2)控制熔湯對流型態以抑制氧雜質進入固液介面、(3)增加氧雜質於自由液面處之氣化量。本研究利用數值模擬方法,透過改變晶體轉速和坩堝轉速,發現堝轉之無因次Richardson數小於晶轉之無因次Richardson數,堝轉是影響氧濃度之重要參數。而過高的堝轉會提升堝壁溫度,不利於降氧,過低的堝轉,會使熔湯對流形態將氧自堝壁向晶棒邊緣區域輸送,不利於降低氧濃度。因此,必須在原有設計中改變堝轉參數,獲得有利於降氧的熔湯流動形態。而增加氬氣流量可增加氣化氧化矽雜質於自由液面處之輸送量。而降低爐壓利於氧化矽雜質於自由液面處之氣化量。除上述改變原有爐體生長參數之控氧方案外,本研究亦設計修改熱場,藉由修改熱遮罩外型,再增加氣化氧化矽雜質於自由液面處之輸送量。本研究也改變加熱器位置,以降低坩堝壁溫度,降低釋氧濃度。除整合前述各種控氧設計概念與最佳的長晶參數外,本研究亦修改爐體熱場,使長晶耗能降低55%,達到節能目的。此最佳爐體設計與生長參數可使氧濃度較原設計爐體長成之晶棒降低29.3%。而提昇晶片品質也是本研究的另一個重點,由於微缺陷會產生OISF-ring,它會與氧結合生成疊差外,製成太陽能電池也會影響該區域電性。基於前述最佳控氧(降氧)設計,亦可將原設計爐體長成之晶棒中OISF-ring向晶棒邊緣延伸23.3%。
摘要(英) The single crystallize-silicon (sc-si) is a major material for solar cell. Oxygen, one of the most important impurities in Czochralski (CZ) system, affects the efficiency of solar cells. There are three general methods to reduce the oxygen concentration in the melt: (1) The magnitude of oxygen released from the quartz crucible is decreased by reducing the temperature of the wall of the quartz crucible. (2) The oxygen transports from the crucible sidewall to the melt-crystal interface is prevented by controlling the flow pattern of the melt. (3) The magnitude of evaporated silicon oxide at the free surface has to be enhanced. In this study, the numerical simulation has been performed to clear the mechanism of oxygen transportation, such as the distribution of oxygen concentration in the melt is related to the crystal rotation rate and crucible rotation rate. The dimensionless Richardson number (Ri) of crucible rotation is smaller than that of crystal one. It means that the crucible rotation rate affects on the distribution of oxygen concentration in the melt very much. The temperature of the crucible is increased by the higher crucible rotation rate, and it is not good for reducing the oxygen concentration in the melt. When the crucible rotation rate is lower, the oxygen is carried from the crucible to the melt-crystal interface by the flow motion of the melt, and it is also not benefit for reducing the oxygen concentration in the melt. Hence, the optimum rotation rate of the crucible can be found to control the flow pattern of the melt for the conventional Cz furnace. Besides, the quantity of the oxygen transportation on the free surface can be increased by increasing the gas flow rate. The magnitude of evaporated silicon oxcide on free surface can be increased by decreasing the furnace pressure. Except the previous methods of adjusting the growth parameters of the conventional Cz furnace, the methods of modifying the hot zone also are proposed in the present study. The shape of the heat shield is modified to carry more quantity of the silicon oxide on the free surface outside the furnace. And the position of the heater is lift in order to reduce the temperature of the crucible. The optimum growth parameters and the modified designs are integrated to a new furnace, and it does not only reduce more oxygen concentration but also control the oxygen concentration. Furthermore, the design of saving power is also developed in this study, and the dipping power is reduced 55% in comparison with the conventional CZ furnace. The new furnace can reduce the oxygen concentration in the crystal 29.3% in comparison with the conventional CZ furnace. In addition, to improve the crystal quality is another concerned issue in this study. The OISF-ring generated by micro-defects is combined with the oxygen, and it becomes a stacking fault and is harmful to the electric property of the solar cell. The new furnace can not only reduce the oxygen concentration 29.3% but also extend the OISF-ring outward the edge of crystal 23.3% in comparison with the conventional CZ furnace.
關鍵字(中) ★ 氧
★ 柴氏法
★ 單晶矽
關鍵字(英) ★ single crystalline-silicon (sc-si)
★ oxygen
★ CZ
論文目次 摘要…………………………………………………………………i
Abstract………………………………………………………………ii
誌謝…………………………………………………………………iv
目錄…………………………………………………………………v
圖目錄………………………………………………………………vii
表目錄………………………………………………………………xi
符號說明……………………………………………………………xii
第一章 緒論………………………………………………………1
1-1 前言……………………………………………………………1
1-2 柴氏長晶法(CZ)介紹…………………………………………1
1-3 文獻回顧………………………………………………………2
1-3-1 氧雜質……………………………………………………2
1-3-2 OISF-ring與氧雜質的關係…………………………………4
1-4 研究動機與目的………………………………………………5
第二章 研究方法…………………………………………………9
2-1 物理系統與基本假設…………………………………………9
2-2 數學模式……………………………………………………10
2-2-1 統御方程式………………………………………………10
2-2-2 邊界條件…………………………………………………12
2-2-3 紊流計算方式..…………………………………………19
2-3 無因次參數…………………………………………………19
2-4 數值方法與網格、收斂條件測試……………………………21
2-4-1 數值方法…………………………………………………21
2-4-2 網格與收斂條件測試……………………………………21
2-5 數值與實驗結果驗證………………………………………22
第三章 結果與討論……………………………………………29
3-1 熱流場與氧雜質分佈討論…………………………………29
3-1-1 原設計爐體熔湯對流型態與氧雜質分佈………………29
3-1-1-1 不同晶體轉速下熔湯對流型態與氧雜質分佈……29
3-1-1-2 不同坩堝轉速下熔湯對流型態與氧雜質分佈……30
3-1-1-3 原始晶體轉速、坩堝轉速下熔湯對流型態與氧雜質分佈……32
3-1-1-4 最佳晶體轉速、坩堝轉速下熔湯對流型態與氧雜質分佈……32
3-1-2 氬氣流量對氧濃度的影響…………………………………33
3-1-3 爐壓對氧濃度的影響………………………………………33
3-1-4 修改熱遮罩外型的影響………………………………34
3-1-5 改變加熱器位置的影響………………………………34
3-1-6 節能設計……………………………………………………35
3-1-7 最佳設計……………………………………………………35
3-2 微缺陷分析…………………………………………………36
3-2-1 原設計爐體長成晶體之微缺陷分析……………………36
3-2-2 最佳設計爐體長成晶體之微缺陷分析析………………36
第四章 結論……………………………………………………………91
參考文獻…………………………………………………………………92
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指導教授 陳志臣(Jyh-chen Chen) 審核日期 2010-7-26
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