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THERMAL STRESS ESTIMATION FOR LARGE DIAMETER SILICON SINGLE CRYSTAL USING MATERIAL PROPERTIES OBTAINED FROM MOLECULAR DYNAMICS METHOD

利用分子动力学方法获得的材料特性估算大直径硅单晶的热应力

基本信息

批准号：
08455064
负责人：
MIYAZAKI Noriyuki
金额：
$ 3.84万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

The following are results of the present research.(1) A molecular dynamics code was developed to calculate thermal expansion coefficient and elastic constants of single crystals. These values for alpha-Fe were successfully obtained up to intermediate temperatures using the molecular dynamics code. At elevated temperatures, stable solutions cannot be obtained, because thermal oscillation becomes large with temperature increase. To obtain thermal expansion coefficient and elastic constants at the elevated temperatures such as the melting point remains unsolved as a future problem.(2) A computer code was developed for simulations of dislocation density in semiconductor bulk crystals during growth process. The Haasen-Sumino model was used as a constitutive equation for single crystals at elevated temperatures. Dislocation density simulations were perfomed using this computer code for Si, GaAs and InP to show the effectiveness of the computer code. The results indicate W-type dislocation density distributions across the diameter in GaAs and InP single crvstals that can be observed in practical Czochralski (CZ) growth of GaAs and InP.This computer code can be used as a powerful tool for research and development of high quality bulk single crystal.(3) The Young's modulus of Si single crystal near the melting point was estimated in accordance with the fact that dislocation-free bulk single crystals with 8-inch diameter are produced commonly by meana of the practical CZ growth. When the Young's modulus obtained from the experimental relation between the critical resolved shear stress and the corresponding strain for Si single crystal was used in the dislocation density simulation of a 8-inch diameter Si single crystal, dislocation-free single crystal was obtained as a result.Therefore, the use of this Young's modulus is recommended for dislocation density simulations for large diameter CZ silicon crystals such as 16-inch diameter crystals.

以下是本研究的结果。(1)开发了计算单晶热膨胀系数和弹性常数的分子动力学程序。使用分子动力学代码成功地获得了α - fe的这些值，直至中间温度。在高温下，不能得到稳定的解，因为随着温度的升高，热振荡变得很大。在较高温度下的热膨胀系数和弹性常数，如熔点等，是一个有待解决的问题。(2)开发了模拟半导体块体晶体生长过程中位错密度的计算机程序。Haasen-Sumino模型被用作单晶在高温下的本构方程。利用该计算机代码对Si、GaAs和InP进行了位错密度模拟，验证了该计算机代码的有效性。结果表明，在GaAs和InP的实际CZ生长中，可以观察到GaAs和InP单晶的w型位错密度分布。该计算机代码可作为研究和开发高质量块状单晶的有力工具。(3)根据实际CZ生长通常产生直径为8英寸的无位错块状单晶的事实，估计了熔点附近Si单晶的杨氏模量。利用由硅单晶的临界分解剪应力与相应应变的实验关系得到的杨氏模量对直径为8英寸的硅单晶进行位错密度模拟，得到无位错的单晶。因此，推荐使用该杨氏模量来模拟大直径CZ硅晶体（如16英寸直径晶体）的位错密度。