# US 5,650,008 A · Method for preparing homogeneous bridgman-type single crystals > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,650,008 A - Document ID: US5650008A - Status: Granted - Kind: A - Application number: 08/564,680 - Filed: 1995-12-01 - Granted: 1997-07-22 - Earliest claimed: 1995-12-01 - Assignees: Advanced Materials Processing, LLC - Inventors: Sindo Kou; Ying Tao - Web page: https://patentgrep.com/patent/US5650008A ## CPC - C30B 29/10: Inorganic compounds or compositions - C30B 11/04: adding crystallising materials or reactants forming it in situ to the melt - C30B 29/40: AIIIBV compounds {wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi} - Y10T 117/10: Apparatus - Y10T 117/1024: for crystallization from liquid or supercritical state - C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract Growth of homogeneous single crystals is carried out by a modified Bridgman-type process using a second melt of a different composition to replenish the first melt of a predetermined composition held in the crystal growth container. By controlling the replenishing rate and suppressing diffusion between the two melts, composition variations in the first melt and hence the growing crystal are compensated. The second melt may be maintained at a predetermined higher temperature than the first melt. The first melt may be agitated during crystal growth by rotation. A liquid encapsulant may be used. ## Claims ### Claim 1 A method for producing homogeneous single crystals comprising the steps of: a. providing in a vertical container a first melt for crystal growth and a second melt of a different composition in a crucible above said first melt; b. cooling said container to initiate crystal growth from said first melt; c. moving a dummy into said crucible to cause said second melt to replenish and compensate for composition variations in said first melt. ### Claim 2 (depends on 1) The method of claim 1 wherein said container is rotated. ### Claim 3 (depends on 1) The method of claim 1 wherein said second melt is kept at a higher temperature than said first melt. ### Claim 4 A method for producing homogeneous single crystals comprising the steps of: a. providing in a vertical container a first melt for crystal growth and a second melt of a different composition in a crucible immersed in said first melt, said crucible having an elongated passageway to suppress diffusion between said melts; b. cooling said container to initiate crystal growth from said first melt; c. increasing the distance between said crucible and the bottom of said container to cause said second melt to leak out through said passageway to replenish and compensate for composition variations in said first melt. ### Claim 5 (depends on 4) The method of claim 4 wherein the length of said passageway is at least 2.sqroot.Dt, where D is the diffusion coefficient and t the time interval from providing said melts to the commencement of replenishing. ### Claim 6 (depends on 4) The method of claim 4 wherein said passageway is tubular. ### Claim 7 (depends on 4) The method of claim 4 wherein said passageway is horizontal. ### Claim 8 (depends on 4) The method of claim 4 wherein there is relative rotational motion between said container and said crucible. ### Claim 9 (depends on 4) The method of claim 4 wherein a liquid encapsulant covers said melts. ### Claim 10 A method for producing homogeneous single crystals comprising the steps of: a. providing in a vertical container a first melt for crystal growth at the bottom and a second melt of a different composition at the top, said melts being separated by a submerged baffle to form a passageway at least 2.sqroot.Dt in length, where D is the diffusion coefficient and t the time interval from providing said melts in said container to when said first melt is to be replenished; b. cooling said container to initiate crystal growth from said first melt; c. increasing the distance between said submerged baffle and the bottom of said container to cause said second melt to go through said passageway to replenish and compensate for composition variations in said first melt. ### Claim 11 (depends on 10) The method of claim 10 wherein a thermocouple is provided to monitor the temperature at the bottom of said submerged baffle. ### Claim 12 (depends on 10) The method of claim 10 wherein said passageway is coil-like in shape. ### Claim 13 (depends on 10) The method of claim 10 wherein said second melt is kept at a higher temperature than said first melt. ### Claim 14 (depends on 10) A method of claim 10 wherein said second melt is covered with a liquid encapsulant. ### Claim 15 A method for producing homogeneous single crystals comprising the steps of: a. providing in a boat a first melt for crystal growth and a second melt of a different composition, said melts being separated by an immersed baffle to form a passageway between said melts; b. cooling said boat to initiate crystal growth from said first melt; c. increasing the distance between said immersed baffle and the cooling end of said boat to cause said second melt to go through said passageway to replenish and compensate for composition variations in said first melt. ### Claim 16 (depends on 15) The method in claim 15 wherein said passageway is at least 2.sqroot.Dt, where D is the diffusion coefficient and t the time interval from providing said melts in said boat to the commencement of replenishing. ### Claim 17 (depends on 15) The method of claim 15 wherein said passageway is formed between said immersed baffle and the inner wall of said boat. ### Claim 18 (depends on 15) The method of claim 15 wherein said passageway is a through hole in said immersed baffle connecting said melts. ### Claim 19 (depends on 15) The method of claim 15 wherein said boat is tilted. ### Claim 20 (depends on 15) The method of claim 15 wherein said second melt is kept at a higher temperature than said first melt.