Numerical Investigation on the Effect of Thermal Gate Moving Rate on Directional Solidification Process

Abstract

The temperature eld distribution during the growth of crystalline silicon by the directional solidi cation (DS) method is an important factor affecting the growth rate, the shape of the melt-crystal (m-c) interface, and thermal stress. To solve the problem of m-c interface convexity at the early stage of crystal growth caused by supercooling at the bottom center of silicon ingot during DS. In this paper, a two-dimensional global transient numerical model based on a large-size ALD-G7 (G7) crystalline silicon ingot furnace is established and experimentally veri ed. Based on the model, the in uence of different bottom thermal gate moving process curves on the convexity of the m-c interface at the early stage was studied, with emphasis on the changes in temperature eld, m-c interface, and thermal stress at the early stage of crystal growth. We have designed three cases, case 1 uses the original moving process curve of bottom thermal gate, case 2 and case 3 adjust the process curve to 0.95 and 0.9 of the original ratio, respectively.The numerical results show that the center cooling condition of silicon ingot and the convexity of the m-c interface are improved with the decreasing of thermal gate moving rate. Compared with case 1, the convexity of case 2 and case 3 is reduced by 55% and 44% on average, respectively.