Method of making a silica crucible in a controlled atmosphere

A method of making a silica glass crucible of the type having a substantially bubble-free inner layer, at least some of which dissolves when semiconductor materials are melted in the completed crucible, the method comprising:

• forming a silica grain layer having an innermost silica grain layer generally in the shape of a crucible having an upwardly directed opening;
• positioning a cover over the opening;
• introducing a gas into the opening beneath the cover;
• drawing the gas through the grain at a first flow rate;
• replacing substantially all of the air in the silica grain layer with the gas;
• sintering the innermost silica grain layer responsive to application of a first level of electric power to a set of electrodes while drawing the gas through the grain at a first flow rate;
• thereafter initiating fusing of the sintered grain and silica grain beneath the sintered grain to form the bubble-free inner layer responsive to substantially increasing the electric power applied to the electrodes above the first level,
• substantially increasing the gas flow rate after initiating fusing of the sintered grain and silica grain beneath the sintered grain, and again substantially increasing the gas flow rate during formation of the bubble-free layer.

A method of making a silica glass crucible of the type having an upwardly directed opening and a substantially bubble-free inner layer, at least some of which dissolves when semiconductor materials are melted in the completed crucible, the method comprising:

• forming a silica grain layer generally in the shape of the crucible having an inner layer corresponding to the bubble-free layer;
• positioning a cover over the opening;
• introducing a gas into the opening beneath the cover;
• displacing ambient atmosphere beneath the cover with the introduced gas;
• drawing the gas through the silica grain layer at a first flow rate;
• replacing substantially all of the air in the silica grain layer with the gas;
• initiating formation of the substantially bubble-free inner layer responsive to application of electric power to a set of electrodes;
• forming a relatively thin portion of sintered silica grain in an innermost portion of the inner layer while drawing the gas through the silica grain layer at the first flow rate;
• thereafter substantially increasing the flow rate of the gas drawn through the silica grain layer to a level above the first flow rate;
• fusing the relatively thin portion of the inner layer and silica grain beneath the relatively thin portion to form the bubble-free layer, and
• substantially increasing the flow rate of the gas drawn through the silica grain layer during fusing the relatively thin portion of the inner layer and silica grain beneath the relatively thin portion.

A method of making a silica glass crucible of the type having an upwardly directed opening and a substantially bubble-free inner layer, at least some of which dissolves when semiconductor materials are melted in the completed crucible, the method comprising:

• forming a silica grain layer generally in the shape of the crucible having an inner layer corresponding to the bubble-free layer;
• positioning a cover over the opening;
• introducing a gas into the opening beneath the cover;
• displacing ambient atmosphere beneath the cover with the introduced gas;
• and
• thereafter sintering an innermost layer of the inner layer responsive to application of a first level of electric power to a set of electrodes while drawing the gas through the silica grain layer responsive to a vacuum pump operating at a first operating level,
• fusing the relatively thin portion of the bubble-free layer with the pump operating at a substantial power increase over the first level of power.