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CZ (CZ) Si晶体生长过程中的热化学反应和高温下的物理现象，注意到(a)熔体和晶体中杂质原子的输运，(b)晶种与生长晶体界面附近的位错行为。典型结果如下：(1)用无底滴法可以精确地得到硅坩埚对硅熔体的氧溶解速率。在硅熔体中大量掺杂的Ge原子与从硅坩埚中溶解的氧原子一起蒸发，蒸发速率随熔体中Ge浓度的增加而增加。(2)通过对比硅晶体中Ge浓度和相应硅熔体中Ge浓度，研究了Ge的偏析系数，在10^<19> ~ 10^<21>原子/cm^3范围内，其偏析系数约为0.48。(3)在不同温度条件下，研究了重b掺杂Si种子中热冲击引起的位错。B浓度越高，放置在熔体表面上方的种子与浸渍时熔体的温差越小，位错就越明显。(4)通过实验和计算研究了重掺杂Si种子与轻掺杂Si生长晶体界面附近晶格失配导致的位错抑制机制。在晶体生长过程中，界面附近的B浓度逐渐发生变化，B原子从重掺杂种子中扩散而形成分布。(5)在生长的晶体中产生了位错，但由于热冲击和晶格失配引起的位错通过使用重B和Ge共掺杂的Si种子来抑制。这种位错是在熔体温度较低的情况下产生的，我们认为位错是由于不完全播种造成的。

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.