Low-contamination AlN crucible for monocrystal pulling and method
AssigneeW. C. Heraeus GmbH
InventorsFritz Aldinger, Richard Keilberth, Waltraud Werdecker
Life of this patent
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Abstract
A low contamination crucible for pulling monocrystals of Group III and Group V elements of the Periodic Table, comprising particularly aluminum nitride with an additive of boron nitride or a rare earth oxide. The additive concentration is up to 5% by weight, but preferably 0.5% to 3% by weight. The hardness of the crucible of the invention is 300 to 400% greater than that of undoped material subjected to the same sintering conditions.
Claims7
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.degree. C.;
- (8) thereafter raising the substantially inert gas pressure to 140 millibars;
- (9) further raising the temperature in said sintering chamber to 1800.degree. C. within one hour and permitting the substantially inert gas pressure to rise to 190 millibars;
- (10) holding said crucible at 1800.degree. C. for two hours;
- and
- (11) allowing the crucible to cool to room temperature.
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.degree. C.;
- (8) thereafter raising the substantially inert gas pressure to 140 millibars;
- (9) further raising the temperature in said sintering chamber to 1800.degree. C. within one hour and permitting the substantially inert gas pressure to rise to 190 millibars;
- (10) holding said crucible at 1800.degree. C. for two hours;
- and
- (11) allowing the crucible to cool to room temperature.
Dependencies are inferred from the claim text.