Global Simulation and Experiments on Oxygen Transport In Silicon CZ furnace

在本研究项目中，我们开发了一个基于数学模型的硅直拉斯基炉整体分析的数值模拟程序，在此模型中，我们假设炉内的流动场、温度场和浓度场为轴对称的伪稳态。这些程序的运行有效地解释了气相扩散和熔体表面的马兰戈尼效应在氧杂质传质中的作用。研究了轴向磁场对氧传质的影响。进一步的数值研究是为了评价热物理性质对传质的影响。数值结果表明，SiO在气相的传质阻力是小型硅Cz炉中最大的传质阻力。然而，氧的传质速率是气体和熔体中速度场和温度场的复杂函数。通过在坩埚和晶体之间加装导气装置，使坩埚内气体沿熔体表面流动，气相传质系数显著提高。这种气体流动在熔体中产生了较大的份额应力，改变了熔体的流动模式，降低了熔体中的传质速率。数值结果表明，表面张力温度系数是决定熔体流动模式的重要因素之一。硅熔体表面张力的详细测量是了解硅Cz炉内输运现象的必要条件，包括气相氧分压的影响。这些数值结果已计划与从NEC公司搬来的小型Cz炉的新实验结果进行比较。搬迁时间原定于2001年，但被推迟到2002年，并于2002年底再次搬迁到九州大学应用力学研究所。从那时起，该炉主要用于氧化晶体的拉拔。因此，我们无法用该炉进行详细的氧输运实验。数值结果与少量实验结果进行了比较。两种数值模拟结果吻合较好，对数值模拟结果有信心。这些全球模拟的结果发表在国际期刊上的5篇论文中。除了这些全局分析之外，我们还报道了3篇关于硅熔体环形池中图案形成的三维模拟的论文。我们发表了一篇关于Cz炉熔体流动对流不稳定性的综述文章。少

In this Research project, we have developed a numerical simulation code for a global analysis of silicon Czochralski furnace based on a mathematical mode, in which we assumed axisymmetric, pseudo steady state of flow, temperature and concentration fields in the furnace. These codes were effectively runned to elucidate the role of gas phase diffusion and the Marangoni effect acting on the melt surface in the mass transfer of oxygen impurity. We have investigated the effects of axial magnetic field on the oxygen mass transfer. Further numerical Investigations have been done so as to evaluate the effect of thermophysical properties on the mass transfer.These numerical results revealed that mass transfer of SiO in the gas phase is the largest mass transfer resistance in a small silicon Cz furnace. However, oxygen mass transfer rate is a complex function of velocity and temperature fields in the gas and melt. By installing a gas guide between the crucible and crystal, whole volume of gas fl … More ows along the melt surface and the gas phase mass transfer coefficient is significantly increased. This type of gas flow give rise of large share stress in the melt and changes the melt flow pattern and decrease the mass transfer rate in the melt. Numerical results indicated that temperature coefficient of surface tension is one of the important factor of determining the melt flow pattern. Detailed measurement of surface tension of silicon melt is necessary to understand the transport phenomena in silicon Cz furnace including the effect of oxygen partial pressure in gas phase.These numerical results had been scheduled to be compared with new experimental results using a small Cz furnace which was moved from NEC company. The time of the moving was originary scheduled on 2001 but it was delayed to 2002 and further moved again to the Institute of Applied Mechanics, Kyushu University on late 2002. Since then the furnace was mostly used for oxide crystal pulling. Thus, we could not conduct detailed experiments of oxygen transport using the furnace. The numerical results were compared with few experimental results. We get confidence on our numerical results of global simulations since both results showed reasonable agreement with each other.The results of these global simulation were reported in 5 papers on International Journals. In addition to these global analyses, we have reported 3 papers on three dimensional simulation of pattern formation in annular pools of silicon melt. We published one review article on the convective instability of melt flow in Cz furnace. Less