Analysis of Structural Development and Defects during the Anisotropic Growth of Silicon.

Abstract

High-performance polysilicon (P-Si) is fundamental as a resource for manufacturing semiconductor devices with high photoelectric properties. However, experimentally characterizing the solidification process in detail has been difficult on account of the extremely rapid cooling rate and limited available characterization methods. Therefore, this study used molecular dynamics (MD) to investigate Si crystallization behavior through directional solidification at different cooling rates. The entire system was first analyzed in terms of energy and radial distribution function, after which the microstructural evolution was characterized by visualization. Results indicated that the cooling rate significantly affected the directional solidification of Si, and an excessively high cooling rate resulted in a decrease in the long-range order of the system. At the same cooling rate, the crystallization rates of (1 0 0), (1 1 0), and (1 1 1) crystal faces followed a descending order. The configurations of the S-L interface with different crystal faces were distinct. Specifically, while the atom numbers of defect structures that were formed in systems of (1 0 0) and (1 1 0) crystal faces were few, those formed in the (1 1 1) crystal face were more. It was difficult for the (1 0 0) crystal face to form dislocations regardless of the crystallization degree at different cooling rates, and the (1 1 0) crystal face only formed a few dislocations at high cooling rates. Dislocations formed at all cooling rates during the directional solidification of the (1 1 1) crystal face, and there was a weak correlation between the number of dislocations and cooling rates. Twinning mainly occurred during the solidification process of the (1 1 1) crystal face, and there was no obvious linear relation between its number and the cooling rate. Moreover, when high-energy dislocations occurred more often, the system stability decreased. Overall, this work will be helpful to understand the commonness and difference in directional solidification of Si with different crystal faces at different cooling rates.