An in-situ observation of dislocations and crystal-melt interface during the melting of silicon

A big issue in the growth of large-diameter silicon crystals is how to grow a dislocation-free crystal without a Dash necking process. The dislocations were generated in touching of the seed crystal with the melt. However, the mechanism of the dislocation generation and removal in the necking process was not clarified yet. Therefore, it is necessary to study the dislocation effect on the melting process of silicon. In-situ observations of the melting process of non-doped silicon samples were performed by an X-ray topographic method. We focused on the dislocation effect on the interface shape between the crystal and the melt during the melting process. The melting processes in different dislocation densities (high density, low density, dislocation-free case) were investigated. Moreover, the melting process with different heating-rates was also studied. The experimental results of the systematic study were summarized and discussed. The melting process in the presence of dislocations is an inhomogeneous process with a rough crystal-melt interface. On the contrary, the dislocation-free melting process is a homogeneous process with a flat interface. Moreover, it was found that the dislocation-free melting process depended on the heating-rate. Dot contrasts appeared during the melting at high heating-rates.