# US 7,611,580 B2 · Controlling melt-solid interface shape of a growing silicon crystal using a variable magnetic field > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,611,580 B2 - Document ID: US7611580B2 - Status: Granted - Kind: B2 - Application number: 11/753,722 - Filed: 2007-05-25 - Published: 2007-10-04 - Granted: 2009-11-03 - Earliest claimed: 2004-12-30 - Assignees: MEMC Electronic Materials, Inc. - Inventors: Zheng Lu - Web page: https://patentgrep.com/patent/US7611580B2 ## CPC - C30B 29/06: Silicon - C30B 15/203: {the relationship of pull rate (v) to axial thermal gradient (G)} - C30B 15/22: Stabilisation or shape controlling of the molten zone near the pulled crystal; Controlling the section of the crystal - C30B 15/305: {Stirring of the melt} - Y10S 117/917: Magnetic - Y10T 117/10: Apparatus - Y10T 117/1032: Seed pulling - Y10T 117/1052: including a sectioned crucible [e.g., double crucible, baffle] - 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 - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract System for controlling crystal growth in a Czochralski crystal growing apparatus. A magnetic field is applied within the crystal growing apparatus and varied to control a shape of the melt-solid interface where the ingot is being pulled from the melt. The shape of the melt-solid interface is formed to a desired shape in response to the varied magnetic field as a function of a length of the ingot. ## Claims ### Claim 1 A system for controlling crystal growth in a crystal growing apparatus, said crystal growing apparatus having a heated crucible including a semiconductor melt from which a monocrystalline ingot is grown according to a Czochralski process, said ingot being grown on a seed crystal pulled from the melt, said melt and said ingot forming a melt-solid interface therebetween, said system comprising: first and second coils positioned near the crucible for applying a cusped magnetic field to the melt; a variable power supply for energizing the coils to produce the magnetic field applied to the melt; and a controller for varying the power supply while the ingot is being pulled from the melt, said variable power supply being responsive to the controller for varying the magnetic field to control cusp position of the magnetic field relative to the melt-solid interface between the melt and the ingot to control a shape of the melt-solid interface, said controlled shape of the melt-solid interface being a function of length of the ingot. ### Claim 2 (depends on 1) The system of claim 1 wherein the variable power supply is responsive to the controller for varying the magnetic field according to one or more of the following types of magnetic field configurations relative to the melt-solid interface: a horizontally dominated asymmetric magnetic field configuration; an axially dominated asymmetric magnetic field configuration; and a substantially symmetric magnetic field configuration. ### Claim 3 (depends on 2) The system of claim 2 wherein the horizontally dominated asymmetric magnetic field produces one or more of the following: a melt-solid interface shape having a flatter concave gull-wing shape relative to the ingot; an increased axial temperature gradient at the melt-solid interface; and a decreased radial variation of the axial temperature gradient in the ingot near the melt-solid interface. ### Claim 4 (depends on 2) The system of claim 2 wherein the axially dominated asymmetric magnetic field produces one or more of the following: a melt-solid interface shape having a more convex shape relative to the ingot; a substantially stable melt flow; and a decreased level of oxygen concentration in the ingot. ### Claim 5 (depends on 1) The system of claim 1 wherein the first coil is positioned higher than the melt-solid interface and the second coil is positioned lower than the melt-solid interface. ### Claim 6 (depends on 5) The system of claim 5 wherein the variable power supply is responsive to the controller for increasing a power distribution in the first coil relative to the second coil to move the cusp position below the melt-solid interface for achieving a horizontally dominated asymmetric magnetic field configuration. ### Claim 7 (depends on 5) The system of claim 5 wherein the variable power supply is responsive to the controller for increasing a power distribution in the second coil relative to the first coil to move the cusp position above the melt-solid interface for achieving an axially dominated asymmetric magnetic field configuration. ### Claim 8 (depends on 5) The system of claim 5 wherein the variable power supply is responsive to the controller for energizing the first and second coils according to a substantially uniform power distribution to move the cusp position near the melt-solid interface for achieving a substantially symmetric magnetic field configuration. ### Claim 9 (depends on 5) The system of claim 5 wherein the controller varies the power supply to selectively adjust a power distribution of the first and second coils as a function of one or more of the following to change the magnetic field intensity thereby moving the cusp position to a particular position above or below the melt-solid interface: length of the ingot; and growth stage of the ingot. ### Claim 10 (depends on 9) The system of claim 9 wherein the growth stage includes one or more of the following: necking; crown; and late-body to end cone growth. ### Claim 11 (depends on 1) The system of claim 1 wherein the controller is responsive to a desired level of oxygen concentration for varying the power supply to selectively adjust the magnetic field to control the shape of the melt-solid interface to produce the desired level of oxygen concentration in the ingot. ### Claim 12 (depends on 1) The system of claim 1 wherein the controller is responsive to a desired level of oxygen radial gradient for varying the power supply to selectively adjust the magnetic field to control the shape of the melt-solid interface to produce the desired level of oxygen radial gradient in the ingot. ### Claim 13 (depends on 1) The system of claim 1 wherein the first and second coils comprise solenoids. ### Claim 14 (depends on 1) The system of claim 1 wherein the variable power supply includes a first coil power supply for energizing the first coil and a second coil power supply for energizing the second coil. ### Claim 15 A system for controlling crystal growth in a crystal growing apparatus, said crystal growing apparatus having a heated crucible including a semiconductor melt from which a monocrystalline ingot is grown according to a Czochralski process, said ingot being grown on a seed crystal pulled from the melt, said system comprising: first and second coils positioned near the crucible for applying a cusped magnetic field to the melt, said magnetic field being based on power distributed to said first and second coils; a first power supply for supplying the first coil with power according to a first power distribution; a second power supply for supplying the second coil with power according to a second power distribution; and a controller for controlling the first and second power supplies while the ingot is being pulled from the melt to produce the magnetic field applied to the melt, said controller controlling the first and second power supplies according to the first and second power distributions, respectively, for varying the magnetic field to control a shape of the melt-interface as a function of length of the ingot. ### Claim 16 (depends on 15) The system of claim 15 wherein the controller controls the first and second power distributions such that the first power distribution is greater than the second power distribution to move the cusp position below the melt-solid interface for achieving a horizontally dominated asymmetric magnetic field configuration. ### Claim 17 (depends on 15) The system of claim 15 wherein the controller controls the first and second power distributions such that the second power distribution is greater than the first power distribution to move the cusp position above the melt-solid interface for achieving an axially dominated asymmetric magnetic field configuration. ### Claim 18 (depends on 15) The system of claim 15 wherein the controller controls the first and second power distributions such that the first and second power distributions are substantially uniform power to move the cusp position near the melt-solid interface for achieving a substantially symmetric magnetic field configuration. ### Claim 19 (depends on 15) The system of claim 15 wherein the controller controls the first and second power distributions, relative to each other, as a function of one or more of the following to change the magnetic field intensity thereby moving the cusp position to a desired position above or below the melt-solid interface: length of the ingot; and growth stage of the ingot. ### Claim 20 A system for producing a monocrystalline semiconductor ingot by a Czochralski process, said system comprising: a crystal growing apparatus having a heated crucible, said crucible containing a semiconductor melt from which the ingot is grown on a seed crystal pulled from the melt, said melt and said ingot forming a melt-solid interface therebetween; first and second coils positioned near the crucible for applying a cusped magnetic field to the melt; a variable power supply for energizing the coils to produce the magnetic field applied to the melt; and a controller for varying the power supply while the ingot is being pulled from the melt, said variable power supply being responsive to the controller for varying the magnetic field to control cusp position of the magnetic field relative to the melt-solid interface between the melt and the ingot for controlling a shape of the melt-solid interface, said controlled shape of the melt-solid interface being a function of length of the ingot.