In Situ Observation of Etching Processes of Silica Glasses by Silicon Melts

In order to investigate etching of silica crucibles by silicon melts during silicon crystal growth, an in situ observation was made on formation of white dots with brown edges, called “brownish rings”, at the silica-silicon melt interface. The formation of brownish rings was found to be influenced by melt temperature, OH concentration in silica glasses and oxygen concentration in silicon melts. The growth of brownish rings shows a linear dependence on dipping time and the growth mechanism is essentially the same as that for the devitrification of silica glasses. These results suggest that in order to control the etching of silica crucibles during silicon crystal growth, it is important to control both properties of silica glass and oxygen concentration in silicon melts.