Low-contamination AlN crucible for monocrystal pulling and method

• US 4,519,966 A
• Filed: 12/20/1983
• Issued: 05/28/1985
• Est. Priority Date: 12/24/1982
• Status: Expired due to Fees

• Current Assignee: WC Heraeus GmbH (Heraeus Holding GMBH)
• Original Assignee: WC Heraeus GmbH (Heraeus Holding GMBH)
• Inventors: Werdecker, Waltraud, Aldinger, Fritz, Keilberth, Richard
• Primary Examiner(s): McCarthy, Helen M.
• Application Number:
  US06/563,647
• Time in Patent Office: 525 Days
• Field of Search: 501/96, 501/98, 264/65, 264/66, 264/56, 264/67, 423/412, 423/290, 156/616 A, 156/DIG. 83, 156/617 SP, 422/249
• US Class Current: 264/633
• CPC Class Codes: C04B 35/581 based on aluminium nitride
• CPC Class Codes: C30B 15/10 Crucibles or containers for supporting the melt
• CPC Class Codes: Y10S 117/90 Apparatus characterized by composition or treatment thereof, e.g. surface finish, surface coating
• CPC Class Codes: Y10T 117/1032 Seed pulling

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.

Claims

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.

2. A low-contamination crucible, made by the method of claim 1, for pulling of monocrystals, particularly semiconductor compounds of Group III and Group V elements.

3. 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.

4. A low-contamination crucible, made by the method of claim 3, for pulling of monocrystals, particularly semiconductor compounds of Group III and Group V elements.

5. The crucible of claim 4, wherein said rare earth oxide comprises a mixture of at least two oxides selected from the group consisting of gadolinium oxide, lanthanum oxide, samarium oxide and yttrium oxide.

6. A method according to claim 3, wherein said rare earth oxide is selected from the group consisting of gadolinium oxide, lanthanum oxide, samarium oxide and yttrium oxide.

7. A low-contamination crucible, made by the method of claim 6, for pulling of monocrystals, particularly semiconductor compounds of Group III and Group V elements.