近年來，能源問題為全世界注意的焦點，電子元件的能源效率更是節能的重點，包 含電動車、太陽光電、風力發電、…等均使用大量的高功率元件，所以大功率半導 體元件為目前半導體產業發展的主要方向。氧化鎵(Ga2O3)具有較大的能隙使其能 承受高溫，而高的擊穿電場使其能承受更高的工作電壓，可在極高功率運作。 Ga2O3可由柴氏長晶法 （Czochralski method）直接液相生長晶體，相較於其他 寬能隙半導體材料如SiC及GaN只能由氣相生長，Ga2O3晶體生長速度較快 ，且較容易生長大尺寸，大幅縮短生長大尺寸晶體的時間。Ga2O3晶體生長過程，晶體內部輻射特性會影響與爐壁之間的輻射冷卻，影響固液界面的形狀，進而影響晶體的外型，而晶體內的熱應力亦受到晶體外型的影響。為了避免生長過程不穩 定產生螺旋形晶體的機率，了解長晶過程固液界面、晶體外型、熱流場及晶體內熱 應力的演變是非常重要的。本研究將結合2D軸對稱和3D混合的模擬模式，完整模擬從晶冠到晶身的晶體生長情形，並觀察高溫氧分解及自由載子熱輻射吸收等現象對晶體生長之影響。探討長晶各階段熔湯的流動行為、溫度與熱應力的分佈情形 ，以期待透過此研究結果，了解Ga2O3晶體生長的原理與機制，建立生長 Ga2O3晶體的熱環境條件。 ;In recent years, the energy problem has become the focus of attention all over the world. The energy efficiency of electronic components is the focus of energy conservation. Electric vehicles, solar photovoltaic, wind power, etc. all use a lot of high-power devices. Gallium oxide (Ga2O3) has a wide energy band gap so that it can withstand high temperatures, and a high breakdown electric field enables it to withstand higher operating voltages. Compared to other wide band gap semiconductor materials such as SiC and GaN, Ga2O3 can grow from the liquid phase. Hence, the crystal growth rate is faster and it is easier to grow large sizes with a higher quality. The Czochralski crystal growth method is commonly used for growing the Ga2O3 crystal. During the growth of Ga2O3 crystal, the radiation characteristics inside the crystal will affect the radiative cooling with the furnace wall, the shape of the solid-liquid interface, and then the shape of the crystal. The thermal stress in the crystal is also affected by the shape of the crystal. In order to avoid the possibility of unstable spiral crystals during the growth process, it is important to understand the evolution of the solid-liquid interface, crystal shape, thermal and flow fields, and thermal stress in the crystal during the growth process. This study will combine 2D axisymmetric and 3D mixed simulation modes to fully simulate the crystal growth from the crown to the crystal body, and observe the effects of high temperature oxygen decomposition and free carrier thermal radiation absorption on crystal growth. The flow behavior, temperature and thermal stress distributions of the molten melt at various stages will be investigated. The results of this research are expected to understand the principle and mechanism of Ga2O3 crystal growth and establish the thermal environment conditions for Ga2O3 crystal growth.
