大晶粒多晶硅铸锭生长的热场设计与模拟

Thermal System Design and Simulation for Growth of Large Grain Multi-crystal Silicon Ingot

为了生长大晶粒的多晶硅铸锭,晶体从形核到后续生长的热场环境控制至关重要。本文首先在侧加热器与散热块之间加一可移动的隔热环。通过向上移动隔热环,并在底部喷射氩气冷却,对生长工艺进行优化控制。然后利用数值模拟,对改进后的生长界面形状、晶体和熔体中的等温线、晶体和熔体的轴向温度分布以及冷却量对生长环境的影响进行分析。模拟结果表明:冷却速率的最佳值在5～15 W/m2之间,且优化后的晶体和熔体中等温线更平坦,晶体轴向温度梯度增大约1.72 K/cm,从而可有效地避免侧壁形核,促进大晶粒的生长,同时提高了生长速率。

In order to grow large grain multi-crystalline silicon in DSS silicon casting, the key process is to control the thermal system for bulk growth. In this study a moving partition block between the side heater and the heat exchanger block is added. By lifting the partition block and adding a jet cooling onthe bottom block, casting process is controlled optimally. Through the numerical simulation, effects of different cooling flux on growth environment are discussed, and then growth interface, isotherm in the melt and crystal, axial temperature distribution in melt and in crystal are modeled. The results indicate：the optimal value of cooling flux is between 5 W/m^2 and 15 W/mE ; for the new design, the isotherms in the melt and crystal become more flat, and the axial temperature gradient in crystal increases about 1.72 K/cm, which are helpful for avoiding nucleation on the crucible wall, obtaining large grain multi-crystal, and also increasing the growth rate.