柴式法生長氧化鋁單晶過程最佳化熱流場之分析

Thermal-fluid Analysis during the Sapphire crystal growth process by using the Cz method

陳建宏(Chien-Hung Chen)

指導教授 ： 陳志臣

國立中央大學/工學院/機械工程學系/碩士(2008年)

摘要

CZ長晶法生長氧化鋁單晶過程中，為了提升氧化鋁單晶的生長品質，必須了解CZ長晶爐內部的熱傳與熔湯流動情形。由於單晶生長過程無法直接觀察熔湯內的熱流場分佈，所以本研究使用有限元素法之COMSOL軟體模擬電磁場、熱場與流場三場耦合之氧化鋁單晶生長過程。RF線圈產生感應電磁場，銥坩堝受到感應電磁場而產生熱源，銥坩堝熱源傳遞到長晶爐內部產生熱場及流場。
本研究主要模擬CZ法生長氧化鋁單晶的生長過程，探討生長過程中熔湯內的熱流場、功率趨勢與晶體固液介面溫梯。為了找出理想的長晶參數，本研究探討不同線圈位置、不同底部絕熱層與不同線圈形狀。以最佳長晶參數做為基準模擬理想氧化鋁單晶生長過程。
結果呈現氧化鋁單晶生長過程中，熔湯內部溫度及速度場會趨於緩和且晶體長度增加固液界面會更凸向熔湯。不同長晶參數部分，底部絕熱層為氧化鋯球、線圈位置在熔湯中心-10mm與線圈形狀為11組小尺寸線圈，所得到的溫梯與功率都為最低。
最後探討不同長晶階段的最佳化線圈位置，並模擬理想晶體生長過程，其功率與各階段溫梯都有下降的趨勢，對於單晶生長品質與節能方面都有較佳的效果。這些分析結果可作為柴氏長晶系統生長氧化鋁單晶時重要參考指標，並可為將來深入研究單晶生長機制的基礎。

關鍵字

CZ法 ； 晶體生長過程 ； 氧化鋁單晶 ； 數值模擬

並列摘要

The thermal and flow transport in a Czochralski crystal growth furnace plays an important role to effect the single crystal growth quality of sapphire. However, the thermal and flow fields in the melt of the single crystal growth process are difficult to observe in experimental study. This thesis has numerically investigated the thermal and flow transport phenomenon using the finite element method via COMSOL Multiphysics software. The electromagnetic, thermal, and fluid fields during the sapphire single crystal growth process have been investigated. The temperature and flow fields inside the furnace are coupled with the heat generation in the Iridium crucible which was generated by the electromagnetic field using the RF coil.
The results presented here demonstrate the effect of different position of coils, different insulator materials of bottom, and different coil forms. The melt temperature and velocity field, power and the temperature gradient distribution during the crystallization have been presented. The results show that the maximum value of the temperature and velocity fields decreases in the melt and the deflection height of the crystal–melt interface increases, as the melt level goes down. In different crystal growth parameter parts, when the ZrO bubble insulator of bottoms is used, the position of coil under the melt center is 10mm and the coil form is 11 groups of small size of coils, the temperature gradient along the crystallization and the input power is lower for the cases considered here. Based on these results, the optimal crystal growth process has been proposed. The results show that the power and the temperature gradient distribution during the crystallization decreases significantly, the single crystal growth quality of sapphire and energy-conservation effect have been improved.

並列關鍵字

CZ method ； crystal growth process ； sapphire ； computer simulation

參考文獻

[1] 劉哲銘,以熱交換器法生長氧化鋁單晶與晶體檢測,國立中央大學機械工程研究所碩士論文(1999).

[3] 朱信旗,電磁式感應加熱柴氏法生長氧化鋁單晶過程之數值模擬分析,國立中央大學機械工程研究所碩士論文(2008).

[4] J. A. Savage, Preparation and properties of hard crystalline materials for optical applications-a review, Journal of Crystal Growth, vol.113, Pages 698-715 (1991).

[6] J. Czochralski, Ein neues Verfahren zur Messung der Kristallisation geschwindigheit der Metalle, Zeitschrift für Physikalische Chemie, vol.92, page 219 (1918).

[7] G. K. Teal and J. B. Little, Growth of germanium single crystals, Physical Review, vol.78, pages 647 (1950).