Low-contamination AlN crucible for monocrystal pulling and method

Claim 1

A method of making a low-contamination crucible for pulling of monocrystals, particularly semiconductor compounds of Group III and Group V elements, consisting essentially of at least 97% by weight aluminum nitride and 0.5% to 3% by weight boron nitride, comprising the steps of: (1) milling a particle mixture of aluminum nitride and hexagonal boron nitride to a powder with a maximum particle diameter of less than 200 micrometers; (2) cold isostatically pressing said powder over a mandrel at a pressure of approximately 2400 bars to form a crucible shape; (3) thereafter placing said crucible shape in a pressure-controlled sintering chamber; (4) evacuating said sintering chamber to a pressure of less than 1 millibar; (5) introducing nitrogen as a substantially inert gas atmosphere; (6) raising the pressure of said substantially inert gas to at least 5 millibars; (7) raising the temperature in said sintering chamber to 1300° C.; (8) thereafter raising the substantially inert gas pressure to 140 millibars; (9) further raising the temperature in said sintering chamber to 1800° C. within one hour and permitting the substantially inert gas pressure to rise to 190 millibars; (10) holding said crucible at 1800° C. for two hours; and (11) allowing the crucible to cool to room temperature.

Claim 2

A method of making a low-contamination crucible for pulling of monocrystals, particularly semiconductor compounds of Group III and Group V elements, consisting essentially of at least 97% by weight aluminum nitride and 0.5% to 3% by weight boron nitride, comprising the steps of: (1) milling a particle mixture of aluminum nitride and hexagonal boron nitride to a powder with a maximum particle diameter of less than 200 micrometers; (2) cold isostatically pressing said powder over a mandrel at a pressure of approximately 2400 bars to form a crucible shape; (3) thereafter placing said crucible shape in a pressure-controlled sintering chamber; (4) evacuating said sintering chamber to a pressure of less than 1 millibar; (5) introducing nitrogen as a substantially inert gas atmosphere; (6) raising the pressure of said substantially inert gas to at least 5 millibars; (7) raising the temperature in said sintering chamber to 1300° C.; (8) thereafter raising the substantially inert gas pressure to 140 millibars; (9) further raising the temperature in said sintering chamber to 1800° C. within one hour and permitting the substantially inert gas pressure to rise to 190 millibars; (10) holding said crucible at 1800° C. for two hours; and (11) allowing the crucible to cool to room temperature.

Claim 4

A method of making a low-contamination crucible for pulling of monocrystals, particularly semiconductor compounds of Group III and Group V elements, consisting essentially of at least 97% by weight aluminum nitride and 0.5% to 3% by weight of a rare earth oxide, comprising the steps of: (1) milling a particle mixture of aluminum nitride and at least one rare earth oxide to a powder with a maximum particle diameter of less than 200 micrometers; (2) cold isostatically pressing said powder over a mandrel at a pressure of approximately 2400 bars to form a crucible shape; (3) thereafter placing said crucible shape in a pressure-controlled sintering chamber; (4) evacuating said sintering chamber to a pressure of less than 1 millibar; (5) introducing nitrogen as a substantially inert gas atmosphere; (6) raising the pressure of said substantially inert gas to at least 5 millibars; (7) raising the temperature in said sintering chamber to 1300° C.; (8) thereafter raising the substantially inert gas pressure to 140 millibars; (9) further raising the temperature in said sintering chamber to 1800° C. within one hour and permitting the substantially inert gas pressure to rise to 190 millibars; (10) holding said crucible at 1800° C. for two hours; and (11) allowing the crucible to cool to room temperature.

Claim 5

A method of making a low-contamination crucible for pulling of monocrystals, particularly semiconductor compounds of Group III and Group V elements, consisting essentially of at least 97% by weight aluminum nitride and 0.5% to 3% by weight of a rare earth oxide, comprising the steps of: (1) milling a particle mixture of aluminum nitride and at least one rare earth oxide to a powder with a maximum particle diameter of less than 200 micrometers; (2) cold isostatically pressing said powder over a mandrel at a pressure of approximately 2400 bars to form a crucible shape; (3) thereafter placing said crucible shape in a pressure-controlled sintering chamber; (4) evacuating said sintering chamber to a pressure of less than 1 millibar; (5) introducing nitrogen as a substantially inert gas atmosphere; (6) raising the pressure of said substantially inert gas to at least 5 millibars; (7) raising the temperature in said sintering chamber to 1300° C.; (8) thereafter raising the substantially inert gas pressure to 140 millibars; (9) further raising the temperature in said sintering chamber to 1800° C. within one hour and permitting the substantially inert gas pressure to rise to 190 millibars; (10) holding said crucible at 1800° C. for two hours; and (11) allowing the crucible to cool to room temperature.