热屏结构对200 mm半导体级提拉单晶硅中氧含量分布的影响

Effect of Heat Shield Structure on the Distribution of Oxygen Content in 200 mm Semiconductor-Grade Czochralski Monocrystalline Silicon

半导体级单晶硅是芯片的基础核心材料,其晶体的氧含量分布对晶圆品质有重要影响。通过优化提拉单晶炉的热屏结构可有效控制晶体生长过程中的氧含量分布,但难以通过实验探究其内在影响机制。本文采用ANSYS有限元分析,研究了热屏结构对200 mm半导体级直拉单晶硅氧含量分布的影响。针对一段式、二段式两种典型的商用单晶炉热屏结构,模拟了拉晶初期(300 mm)、中期(800 mm)、末期(1000 mm)三个等径阶段的温度场、流场分布,固液界面温度梯度及径向氧含量分布。计算结果表明,与二段式热屏相比,一段式热屏的熔体温度场均一性较好,固液界面的温度梯度较小。此外,一段式热屏的氩气流场有利于熔体自由表面上方SiO气体挥发和减弱熔体的剪切对流,使固液界面前端向晶体扩散的氧减少。因此,一段式热屏的固液界面径向氧含量分布均匀性较好且晶体中的氧含量较低。

Semiconductor-grade monocrystalline silicon is the basic material for the integrated circuit industry and its quality determines the performance of chips.The distribution of oxygen content in Czochralski(Cz)silicon crystals has an important impact on the quality of silicon wafers.The oxygen content distribution during crystal growth can be effectively controlled by optimizing the heat shield structure of the furnace,but it is difficult to investigate the intrinsic mechanism through experiments.In this study,effect of the structure of heat shield on the distribution of oxygen content in 200 mm semiconductor-grade Cz monocrystalline silicon was investigated by ANSYS finite element analysis.Single-section and two-section heat shield structures are widely used in commercial furnace,by comparison,the distribution of temperature and flow fields,the temperature gradient at the solid-liquid interface and the radial oxygen content distribution for different stages of body growth(300,800,1000 mm)were analyzed.The simulation results demonstrate that the temperature field uniformity of the single-section heat shield structure is better than that of the two-section heat shield structure,the temperature gradient at the solid-liquid interface in the former is smaller.Also,the low argon flow rate is favorale to the volatilization of SiO gas,and weakening the shear convection of the melt,leading to an inhibition of diffusion movement of oxygen from melt to crystal.Therefore,the radial oxygen content distribution at the solid-liquid interface is more uniform and the oxygen content in the crystal is lower under the condition of the single-section heat shield structure than that of the two-section heat shield structure.