【摘要】 采用数值模拟的方法研究了微重力条件下Czochralski法生长硅晶体过程中熔体热毛细对流的基本特征,探讨了水平和垂直温度梯度的耦合对熔体流动的影响。熔体自由表面与外界辐射换热,水平温度梯度Marangoni(Ma)数选取(0~3 000),底部热流Q选取(1.39×10-2~1.76×10-2)。结果表明,当Q和Ma数均较小时,流动为稳态,液池内产生3个流胞,熔体流动由Q主导,减小Q或增大Ma数可使流动更稳定。当Ma数增大到一定值时,流动从稳态转变为非稳态,流动的临界Mac数随Q的增大而显著减小。流动失稳后,出现了新的流动转变方式,Ma数为影响表面波动形式的关键因素,Q会改变热流体波数,是晶体附近的热流体波产生的决定因素。随着Ma数和Q的不断增强,自由表面最终形成弯曲条幅状热流体波。更多还原

【Abstract】 The bidirectional temperature gradients play an important part in the convection of crystal growth.However,most of the researches before only focused on unidirectional temperature.In this paper,under microgravity,a serious of numerical simulations was conducted to study the thermocapillary convection in Czochralski growth of silicon crystal.The coupling effects of vertical and horizontal temperature gradients were discussed.The radiation on the melt surface was considered,the range of horizontal and vertical temperature gradient were Ma=(0-3000)and Q=(1.39×10-2-1.76×10-2)respectively.Results show that flow is steady for small Qand Ma.In this case,there are three flow cells in the melt,the melt flow is dominated by Q;the flow is more stable due to the decrease of the Q and the increase of the Ma.When the Ma exceeds a threshold value,an unsteady three dimensional flow is developed.With the increase of the Q,the critical Ma significantly decreased.When the flow is unsteady,a new way of the flow pattern transtion is found.Mais the key for the change of the surface fluctuation pattern.The number of the hydrothermal wave is changed by Q,and the generation of hydrothermal wave which is near the crystal is determined by Q.With the enhancement of the Qand Ma,the flow pattern enventually changes into curved spoke patterns.更多还原