US Patent 7383696 Silica glass crucible with bubble-free and reduced bubble growth wall

A silica glass crucible includes a stable, bubble-free inner layer and an opaque outer layer, both layers demonstrating reduced bubble growth during a Czochralski process. When used in the CZ process, little volume change is observed in the crucible wall, and the crucible has little influence on melt level. The present crucible is especially suited for slow silicon ingot pulling with reduced crystalline defects. The fusion process of the present invention controls the dynamic gas balance at the fusion front where formed grain is melted to dense fused silica.