Growth of bulk single crystals of aluminum nitride from a melt

• US 5,954,874 A
• Filed: 10/06/1997
• Issued: 09/21/1999
• Est. Priority Date: 10/17/1996
• Status: Expired due to Term

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Hunter, Charles Eric
• Primary Examiner(s): HITESHEW, FELISA CARLA
• Application Number:
  US08/944,393
• Time in Patent Office: 715 Days
• Field of Search: 117/84, 117/87, 117/88, 117/99, 117/952
• US Class Current: 117/84
• CPC Class Codes: C30B 15/00 Single-crystal growth by pulling from a melt, e.g. Czochralski method under a protective fluid C30B27/00
• CPC Class Codes: C30B 15/02 adding crystallising materials or reactants forming it in situ to the melt
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: Y10T 117/10 Apparatus
• CPC Class Codes: Y10T 117/1004 with means for measuring, testing, or sensing
• CPC Class Codes: Y10T 117/1008 with responsive control means

Abstract

Large diameter single crystals of aluminum nitride (AlN) are grown isotropically by injecting a nitrogen-containing gas into liquid aluminum at elevated temperatures. A seed crystal that is maintained at a temperature below that of the surrounding liquid aluminum is pulled from the melt, while the AlN that is formed in the melt is deposited on the seed crystal. An apparatus for carrying out the method is also disclosed.

Claims

1. A method for producing a bulk single crystal of AlN comprising the steps of:

contacting nitrogen with a melt of liquid Al to form AlN in the melt;

while

depositing the AlN so formed in single crystalline form on a seed crystal that is in physical contact with the melt.

2. The method of claim 1 wherein the nitrogen is in the form of a nitrogen-containing gas.

3. The method of claim 1 wherein the nitrogen is in a solid nitrogen-containing compound.

4. The method of claim 3 wherein the nitrogen is in the form of AlN.

5. The method of claim 4 wherein the AlN is pressed AlN powder.

6. The method of claim 1 comprising the step of depositing AlN on the seed crystal at a crystal growth rate greater than about 0.5 mm per hour.

7. The method of claim 6 wherein the bulk single crystal of AlN is grown with a diameter greater than one inch.

8. The method of claim 1 wherein the melt is pure Al.

9. The method of claim 1 wherein the melt comprises an Al-containing compound.

10. A method for producing a bulk single crystal of AlN comprising the steps of:

flowing a nitrogen-containing gas into a melt of Al to form AlN in the melt;

while

depositing the AlN so formed in single crystalline form on a seed crystal that is pulled from the melt.

11. The method of claim 10 wherein the nitrogen-containing gas is predominately N₂.

12. The method of claim 10 including the step of pulling the seed crystal at a rate greater than about 0.5 mm per hour.

13. The method of claim 10 wherein the step of flowing a nitrogen-containing gas into the melt is performed by injecting the gas into the melt below the seed crystal.

14. The method of claim 10 wherein the melt is contained in a crucible with a surrounding chamber pressure on the order of 3000 torr.