| 摘要: | 氧化鎵（Ga2O3）是新型的氧化物半導體，氧化鎵寬能隙的材料性
質，具備開發為高效率電子元件的潛能，再加上 β-Ga2O3可經由液相長
晶法進行生長，與氣相長晶法相比，能夠大幅的提升長晶的速率以及晶
體的品質。由於長晶過程中，晶體與熔湯間固液介面的形狀與位置影響
著晶體成形的穩定度，而腔體的溫場與熔湯的流場則進一步影響著介面
的位置與能量的平衡，因此在長晶的過程中溫場與流場的控制相當重要。
本研究以數值方法進行模擬柴氏法 Czochralski（Cz）生長氧化鎵晶
體過程中晶體-熔湯之固液介面形狀與位置，透過改變感應加熱線圈的
間距、位置以及功率大小來模擬並分析熱場、流場，最後依據晶體-熔湯
間固液介面上的熱通量差值進行介面幾何位置的調整直至收斂。
從研究中發現腔體的溫場與流場會影響介面的能量平衡，在固定拉
速的條件下，感應加熱線圈的功率、位置會影響介面的凹凸程度，根據
文獻回顧，凸向熔湯的介面較容易生長出完整的晶棒，本研究結果中可
以得知，熔湯的流場型態由浮力渦流所主導，等溫線受對流影響而變形，
為了達成介面的能量平衡，隨著輸入功率提高，固液介面形狀朝向晶體
方向變化，並且功率過高，介面形狀會由低功率的凸向熔湯變成凹向熔
湯；提高線圈位置會造成固液介面軸向變化增加，並且線圈位置越高固
液介面於熔湯中凸率增加；加大線圈間距使得熔湯溫度下降，固液介面
於熔湯中凸率增加，並且線圈間距過大時，會造成熔湯溫度低於熔點溫
度。;Gallium oxide (Ga2O3) is a new material of oxide semiconductor . For
the wide Band-gap material property , Gallium oxide has the potential to
develop as efficient electro components. Compare with growing from the gas
phase, β-Ga2O3 crystals could be grown from liquid phase and also have
higher growth rate as well as better quality. The temperature field of the cavity
and the melt flow affect the crystal-melt interface shape and energy balance .
And also the crystal-melt interface shape will affect the stability of crystal
formation during crystal growth . Therefore the control of the crystal growth
temperature field and melt convection is very important .
This study analyzes the crystal-melt interface shape and position when
the Ga2O3 crystal grows in Czochralski method through numerical
simulation . In the simulation , we change coils spacing and position of
induction heating coil and also the input power to see the difference in the
result . Last, according to the heat flux difference , on the crystal-melt
interface , to adjust the interface geometric position till convergence .
The results show that the temperature field and flow field in the crystal
growth furnace will affect the energy balance on the crystal-melt interface .
Under the condition of fixed crystal pulling speed , the spacing and position
of heating coils will cause different degrees of unevenness of the interface .
Based on reference reviews , the interface convex to the melt is easier to grow
complete crystals . Known from the simulation result , the flow field pattern
in the melt is dominated by buoyant force, and the isotherm line is deformed
by convection. In order to reach the energy balance on the crystal-melt
interface, when the input power increases, the shape of the interface will
change towards the crystal direction.
IV
In addition, when the power is too high, the interface shape will change
from convex to concave . The second result is that the higher the coil position,
the higher the convexity of the interface in the melt . Furthermore, increasing
the position of the coil will increase the axial variation of the crystal-melt
interface. Third result is the expansion of coil spacing , which will lower the
temperature of the melt and cause the interface to increase the convexity in
the melt . When the coil spacing is too large, the melt temperature will be
lower than the melting point temperature. |
