# US 5,352,615 A · Denuding a semiconductor substrate > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,352,615 A - Document ID: US5352615A - Status: Granted - Kind: A - Application number: 08/185,351 - Filed: 1994-01-24 - Granted: 1994-10-04 - Earliest claimed: 1994-01-24 - Assignees: Motorola, Inc. - Inventors: Young Limb; Philip J. Tobin - Web page: https://patentgrep.com/patent/US5352615A ## CPC - H10P 72/0436: {mainly by radiation} - C30B 33/00: After-treatment of single crystals or homogeneous polycrystalline material with defined structure (C30B31/00 takes precedence) - H10P 36/20: Intrinsic gettering, i.e. thermally inducing defects by using oxygen present in the silicon body - Y10S 148/06: Gettering - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - 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 - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A semiconductor substrate is denuded using a reducing gas mixture including carbon monoxide and carbon dioxide. Use of the reducing gas mixture allows very low oxygen partial pressure to be achieved in a furnace tube during the step of denuding. Oxygen partial pressure lower than 1E-9 atmosphere may be achieved by adjusting the relative ratio of carbon monoxide and carbon dioxide. Precipitates are grown after forming nucleating sites. Both CZ and FZ substrates may use the process, and the process can be used with silicon, germanium, or other semiconductor materials. ## Claims ### Claim 1 A process for forming a denuded zone within a semiconductor substrate comprising the steps of: providing the semiconductor substrate having a primary surface and an oxygen concentration in a region adjacent to the primary surface; heating the substrate to a first elevated temperature in a reducing ambient that includes carbon-containing molecules to lower the oxygen concentration within the region. ### Claim 2 (depends on 1) The process of claim 1, further comprising steps of: adjusting the temperature of the substrate to a second elevated temperature that is lower than the first elevated temperature; and maintaining the substrate at the second elevated temperature for a time to form nucleating sites for precipitates, wherein: the sites are formed within the bulk of the substrate; and the region lies between the bulk and the primary surface. ### Claim 3 (depends on 2) The process of claim 2, wherein the first elevated temperature is at least 1000 degrees Celsius and the second elevated temperature is in a range of 450-850 degrees Celsius. ### Claim 4 (depends on 2) The process of claim 2, wherein: at the step of providing, the region has an oxygen concentration of about 5-50 parts per million; and after the step of maintaining, the region has an oxygen concentration of less than one part per million. ### Claim 5 (depends on 2) The process of claim 2, further comprising steps of: adjusting the temperature of the substrate to a third elevated temperature that is higher than the second elevated temperature; and maintaining the substrate at the second elevated temperature to grow precipitates from the nucleating sites. ### Claim 6 (depends on 5) The process of claim 5, wherein the third elevated temperature is at least 800 degrees Celsius. ### Claim 7 (depends on 1) The process of claim 1, wherein the reducing ambient includes carbon monoxide and carbon dioxide. ### Claim 8 (depends on 7) The process of claim 7, wherein the reducing ambient includes at least one part of carbon monoxide for every 50 parts of carbon dioxide. ### Claim 9 (depends on 1) The process of claim 1, wherein the reducing ambient has no higher than one part per million of oxygen. ### Claim 10 (depends on 1) The process of claim 1, wherein the reducing ambient includes a gas selected from a group consisting of argon, helium, nitrogen, and hydrogen. ### Claim 11 (depends on 1) The process of claim 1, wherein the region is at least three microns thick. ### Claim 12 A process for forming a denuded zone within a silicon substrate comprising the steps of: providing the silicon substrate having a primary surface and an oxygen concentration in a region adjacent to the primary surface that is about 5-50 parts per million; heating the substrate to a first elevated temperature that is at least 1000 degrees Celsius for about 1-4 hours in a reducing ambient that includes carbon monoxide and carbon dioxide; lowering the temperature of the substrate to a second elevated temperature that is about 450-850 degrees Celsius; and maintaining the substrate at the second elevated temperature for a time to form nucleating sites for oxygen precipitates within the bulk of the substrate, wherein the region lies between the bulk and the primary surface. ### Claim 13 (depends on 12) The process of claim 12, wherein after the step of maintaining, the region has an oxygen concentration in the region of less than one part per million. ### Claim 14 (depends on 12) The process of claim 12, wherein the reducing ambient includes at least one part of carbon monoxide for every 50 parts of carbon dioxide. ### Claim 15 (depends on 12) The process of claim 12, wherein the reducing ambient has no more than one part per million of oxygen. ### Claim 16 (depends on 12) The process of claim 12, wherein the reducing ambient includes a gas selected from a group consisting of argon, helium, nitrogen, and hydrogen. ### Claim 17 (depends on 12) The process of claim 12, further comprising steps of: adjusting the temperature of the substrate to a third elevated temperature that is higher than the second elevated temperature; and maintaining the substrate at the second elevated temperature to grow precipitates from the nucleating sites. ### Claim 18 (depends on 12) The process of claim 12, wherein the region is at least three microns thick.