Experimental and numerical investigation of the horizontal ribbon growth process

Abstract

Experimental and numerical results are presented on the process of horizontal ribbon growth (HRG) of single-crystal silicon. Experimental data on the leading edge position of the growth front as a function of pull speed is compared to model predictions with and without solidification kinetic effects. Without kinetics, the numerical results predict leading edge positions which are completely different than that observed in the experiment. With kinetics, the leading edge position is predicted typically within 1mm and the change in position with pull speed also is well predicted. Conclusions from the kinetic model are that the growth occurs through a faceted process where the leading edge is a {111} facet that requires significant supercooling to maintain the growth. An outcome of the model is that the leading edge position versus pull speed response shows a turning point beyond which there are no steady growth solutions. This is consistent with all previously reported experiments on this process, which have reported maximum attainable pull-speeds. These results directly contradict previous conclusions from the “wedge” model of horizontal ribbon growth, which predicts that a large area wedge-shaped growth region exists and that increasing pull speeds simply result in a narrower wedge angle.