Melting of Silicon Crystals and a Possible Origin of Swirl Defects

Abstract Melting and growth processes of thin crystals were investigated by in situ X-ray topographic observation. Dislocated crystals were found to melt homogeneously from their surfaces. Droplets of the silicon liquid (locally molten regions) were observed inside dislocation-free crystals, simultaneously with melting from their surfaces. After cooling from the melting process, microdefects were detected at the positions of the droplets by etching and transmission topography. Impurity hydrogen was found to suppress growth of the defects in size after solidification of the droplets. The formation process of the microdefects initiated from the droplet formation is explained by assuming some kinds of impurities which act as absorption centers for infrared radiation penetrating the crystals. As an origin of swirl defects in bulk crystals, the possibility of droplet formation near the growth interfaces during remelting periods is suggested.