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在大尺寸直拉硅单晶生长过程中,针对水平磁场单方向磁力线分布引起的熔体温度分布非轴对称特征,提出了一种双磁力线结构的磁场——四极磁场。为准确描述非轴对称磁场作用下晶体生长过程,采用三维数值模拟方法,建立了四极磁场下二维/三维混合热场模型的边界条件,并将三维数值模拟结果与水平磁场作以对比。结果表明,四极磁场降低了熔体内部温度的非轴对称性;增加磁感应强度有利于增加熔体自由表面附近温度分布的均匀性,但对固液界面形状调节作用不明显;强磁场环境下,提高晶体旋转速度有利于改变固液界面凹凸程度,改善固液界面形态的非轴对称性。
In the process of large-size Czochralski silicon growth, a magnetic field-quadrupole magnetic field with a double magnetic field line structure is proposed for the non-axisymmetric melt temperature distribution caused by the unidirectional magnetic field distribution in the horizontal magnetic field. In order to accurately describe the crystal growth process under the non-axisymmetric magnetic field, the boundary conditions of the two-dimensional / three-dimensional hybrid thermal field model under quadrupole magnetic field are established by three-dimensional numerical simulation method. The three-dimensional numerical simulation results are compared with the horizontal magnetic field. The results show that the quadrupole magnetic field decreases the non-axisymmetry of the internal temperature of the melt. Increasing the magnetic flux density can increase the uniformity of the temperature distribution near the free surface of the melt, but has no obvious effect on the shape regulation of the solid-liquid interface. , Increasing the rotational speed of the crystal is conducive to changing the degree of concavity and convexity of the solid-liquid interface and improving the non-axisymmetry of the solid-liquid interface.