Patent ID: 7497907

Claim:
A crucible holding melted semiconductor material, the crucible comprising: a body of vitreous silica having an open top, a bottom and a sidewall extending up from the bottom, the bottom and sidewall defining a cavity holding the semiconductor material in the crucible below a level of the melted semiconductor material, the sidewall having an inner surface, an outer surface, an enhanced stiffness sidewall portion and a stress accommodating sidewall portion at least part of which is positioned below said enhanced stiffness sidewall portion, the enhanced stiffness sidewall portion being at least partially devitrified and the stress accommodating sidewall portion being substantially free of devitrification so that the stress accommodating sidewall portion accommodates stress in the sidewall, wherein at least one of said inner and outer surfaces of the sidewall includes at least part of both said enhanced stiffness sidewall portion and said stress accommodating sidewall portion, and wherein the body of the crucible is substantially free of enhanced stiffness sidewall portions below the level of the melted semiconductor material.