Thermal control for formation and processing of aluminum nitride
AssigneeCrystal IS, Inc.
InventorsRobert T. Bondokov, Jianfeng Chen, Keisuke Yamaoka, Shichao Wang, Shailaja P. Rao, Takashi Suzuki, Leo J. Schowalter
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Abstract
In various embodiments, controlled heating and/or cooling conditions are utilized during the fabrication of aluminum nitride single crystals and aluminum nitride bulk polycrystalline ceramics. Thermal treatments may also be utilized to control properties of aluminum nitride crystals after fabrication.
Claims24
A method of improving ultraviolet (UV) transparency of a single-crystal AlN bulk crystal, the method comprising:
- heating the AlN bulk crystal to an annealing temperature of at least 2000° C.;
- thereafter, cooling the AlN bulk crystal via a cooling cycle comprising:
- (i) cooling the AlN bulk crystal from the annealing temperature to a first temperature ranging from 1450° C. to 2150° C. over a first time ranging from 10 minutes to 90 minutes, and (ii) thereafter, cooling the AlN bulk crystal from the first temperature to a second temperature ranging from 1000° C. to 1650° C. over a second time ranging from 10 seconds to 10 minutes, or
- (i) cooling the AlN bulk crystal from the annealing temperature to a third temperature ranging from 1450° C. to 2150° C. over a third time ranging from 10 seconds to 10 minutes, and (ii) thereafter, cooling the AlN bulk crystal from the third temperature to a fourth temperature ranging from 1000° C. to 1650° C. over a fourth time ranging from 10 minutes to 90 minutes;
- and
- thereafter, cooling the AlN bulk crystal to approximately room temperature.
A method of improving ultraviolet (UV) transparency of a single-crystal AlN bulk crystal, the method comprising:
- forming the AlN bulk crystal via vapor-phase growth within a crystal-growth apparatus;
- removing the AlN bulk crystal from the crystal-growth apparatus;
- within an annealing apparatus different from the crystal-growth apparatus, heating the AlN bulk crystal to an annealing temperature of at least 2000° C.;
- thereafter, cooling the AlN bulk crystal via a cooling cycle comprising:
- cooling the AlN bulk crystal from the annealing temperature to a first temperature ranging from 1000° C. to 1650° C. over a time period ranging from 1 hour to 10 hours;
- and
- thereafter, cooling the AlN bulk crystal to approximately room temperature.
A method of forming a polycrystalline AlN source, the method comprising:
- providing a bulk polycrystalline AlN ceramic;
- disposing at least a portion of the AlN ceramic into a crucible;
- annealing and densifying the at least a portion of the AlN ceramic in the crucible, thereby forming a polycrystalline AlN source, the annealing and densifying comprising:
- (i) heating the at least a portion of the AlN ceramic at a first temperature ranging from 1100° C. to 1900° C. for a first time ranging from 2 hours to 25 hours, and (ii) thereafter, heating the at least a portion of the AlN ceramic at a second temperature ranging from 1900° C. to 2250° C. for a second time ranging from 3 hours to 15 hours, or
- (i) heating the at least a portion of the AlN ceramic during a temperature ramp to a third temperature ranging from 1900° C. to 2250° C. over a third time ranging from 5 hours to 25 hours, and (ii) thereafter, heating the at least a portion of the AlN ceramic at a fourth temperature ranging from 1900° C. to 2250° C. for a fourth time ranging from 3 hours to 25 hours;
- and
- cooling the AlN source to approximately room temperature.
Dependencies are inferred from the claim text.