Single-crystal pulling apparatus and single-crystal pulling method

Patent metadata

Field	Value
Publication number	US-2023175166-A1
Application number	US-202017605399-A
Country	US
Kind code	A1
Filing date	Mar 19, 2020
Priority date	May 8, 2019
Publication date	Jun 8, 2023
Grant date	—

Abstract

The present invention is a single-crystal pulling apparatus including: a pulling furnace which has a heater and a crucible arranged and which has a central axis; and a magnetic field generation device having superconducting coils, where the magnetic field generation device has four of the superconducting coils, two of the superconducting coils are arranged in each of two regions divided by a cross section that includes an X axis, the X axis being a direction of lines of magnetic force at the central axis in the horizontal plane including all the coil axes of the four superconducting coils, and includes the central axis of the pulling furnace so as to have line symmetry about the cross section, the four superconducting coils are all arranged so that the coil axes have an angle within a range of more than −30° and less than 30° relative to a Y axis, the direction of the lines of magnetic force thereof have line symmetry about the cross section, and in each of the regions, the two superconducting coils generate lines of magnetic force in opposite directions. This provides a single-crystal pulling apparatus with which there is no need to move the magnetic field generation device when dismantling and setting up the single-crystal pulling apparatus, and the oxygen concentration in the single crystal to be grown can be reduced, and at the same time, growth striations in the single crystal to be grown can be suppressed.

First claim

1 . A single-crystal pulling apparatus comprising:
a pulling furnace which has a heater and a crucible containing a molten single crystal material arranged therein, and which has a central axis; and a magnetic field generation device which is arranged around the pulling furnace and has superconducting coils and a cryostat incorporating the superconducting coils, the single-crystal pulling apparatus applying a horizontal magnetic field to the molten single crystal material by energization to the superconducting coils to suppress convection of the molten single crystal material in the crucible, wherein the magnetic field generation device has four of the superconducting coils, all coil axes of the four superconducting coils being arranged so as to be included in a single horizontal plane, when a direction of lines of magnetic force at the central axis in the horizontal plane is determined as an X axis, two of the superconducting coils are arranged in each of a first region and a second region divided by a cross section that includes the X axis and the central axis of the pulling furnace, the four superconducting coils are arranged to have line symmetry about the cross section, the four superconducting coils are all arranged so that the coil axes have an angle within a range of more than −30° and less than 30° in the horizontal plane relative to a Y axis, the Y axis being perpendicular to the X axis, the direction of the lines of magnetic force generated by the four superconducting coils have line symmetry about the cross section, and in each of the first region and the second region, the two superconducting coils generate lines of magnetic force in opposite directions.

2 . The single-crystal pulling apparatus according to claim 1 , wherein the magnetic field generation device comprises, as the cryostat: a U-shaped cryostat incorporating all the four superconducting coils; or a cryostat incorporating two of the superconducting coils in each of the first region and the second region, the two cryostats having a structurally coupled structure.

3 . The single-crystal pulling apparatus according to claim 1 or 2 , wherein a height of the superconducting coils in a vertical direction is greater than a width of the superconducting coils seen from above in a vertical direction.

4 . A single-crystal pulling method comprising pulling a silicon single crystal by using the single-crystal pulling apparatus according to claims 1 to 3 .

Assignees

• Shinetsu Handotai Kk

Inventors

• Takano Kiyotaka
• Yajima Wataru
• Sugawara Kosei
• Kamada Hiroyuki
• Ohta Tomohiko

Classifications

• C30B29/06 Primary

  Silicon · CPC title

• C30B15/305

  Stirring of the melt · CPC title

• C30B30/04

  using magnetic fields · CPC title

• C30B15/20 Primary

  Controlling or regulating (controlling or regulating in general G05) · CPC title