Study of non-equilibrium thermochemical reaction between Si melt and silica glass at high temperature in Czochralski Si crystal growth

本文研究了直拉（CZ）Si晶体生长过程中的热化学反应和高温物理现象，发现（a）杂质原子在熔体和晶体中的输运，（B）籽晶与生长晶体界面附近的位错行为。典型结果如下：（1）用座滴法可以精确地获得氧从石英坩埚向硅熔体的溶解速率。通过比较硅单晶和相应硅熔体中锗的浓度，研究了锗的偏析系数，发现在硅单晶中锗浓度为10 ~ 10atoms/cm ~ 3时，锗的偏析系数约为0.48<19><21>。(3)研究了不同温度条件下重掺硼硅籽晶中热冲击引起的位错。当籽晶中B浓度较大且籽晶与熔体表面温差较小时，位错能得到抑制。(4)通过实验和计算研究了重掺硼硅籽晶与轻掺硼硅单晶生长界面附近晶格失配对位错的抑制机制。界面附近的B浓度在晶体生长过程中逐渐变化，这种分布是由重掺B籽晶中的B原子扩散形成的。(5)虽然通过使用重B和Ge共掺杂的Si籽晶抑制了由于热冲击和晶格失配引起的位错，但是在生长的晶体中产生了位错。这种位错产生的情况下，较低的熔体温度，我们得出的结论是，位错是由于不完全播种。

In this study, the thermochemical reactions and the physical phenomena at high temperature during Czochralski (CZ) Si crystal growth have been investigated, and we noticed (a) transportation of impurity atoms in the melt and the crystal, and (b) the dislocation behavior near the interface between seed and the grown crystal. Typical results are as follows;(1) Oxygen dissolution rate from silica crucible to Si melt could be obtained precisely by sessile drop method. Ge atoms heavily doped in Si melt were evaporated with oxygen atoms dissolved from silica crucible and the evaporation rate increased with increasing Ge concentration in the melt(2) Segregation coefficient of Ge was investigated by comparing Ge concentrations in Si crystal and in corresponding Si melt, and it was about 0.48 with Ge concentration in the crystal in the range from 10^<19> to 10^<21> atoms/cm^3.(3) Dislocation due to thermal shock in heavily B-doped Si seed was investigated under different temperature conditions. The dislocation could be suppressed when B concentration in the seed was larger and temperature difference between the seed placed just above the melt surface and the melt on dipping was smaller.(4) Dislocation suppression mechanism due to lattice misfit near the interface between heavily B-doped Si seed and lightly B-doped Si grown crystal was investigated experimentally and computationally. B concentration near the interface was gradually changed and the distribution was formed by diffusion of B atoms from the heavily B-doped seed during the crystal growth.(5) Dislocations were generated in the grown crystal although the dislocations due to both thermal shock and lattice misfit were suppressed by using a heavily B and Ge codoped Si seed. Such dislocation was generated in the case of lower melt temperature, and we conclude that the dislocation was due to incomplete seeding.