Method of producing silicon single crystal

Patent metadata

Field	Value
Publication number	US-9708731-B2
Application number	US-201615010769-A
Country	US
Kind code	B2
Filing date	Jan 29, 2016
Priority date	Dec 13, 2010
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

A method of producing a silicon single crystal is provided. The method may include taking a real image of a heat shield including a circular opening and a mirror image of the heat shield reflected on a surface of the silicon melt, measuring a spacing between the real image and the mirror image, calculating a position of the surface of the silicon melt, taking an image of a bright zone that appears in a vicinity of an interface between the silicon melt and the silicon single crystal, calculating a position of the surface of the silicon melt based on a center position of the silicon single crystal determined from the image of the bright zone, and controlling the position of the surface of the silicon melt during a pulling of the silicon single crystal while referring to data of the calculated positions of the surface of the silicon melt.

First claim

What is claimed is:

1. A method of producing a silicon single crystal, comprising pulling a silicon single crystal from a silicon melt formed in a crucible, the method comprising:
performing a first operation, with an imaging device, including taking a real image of a heat shield including a circular opening and a mirror image of the heat shield reflected on a surface of the silicon melt, measuring a spacing between the real image and the mirror image, and calculating a position of the surface of the silicon melt;
performing a second operation, with the imaging device, including taking an image of a bright zone that appears in a vicinity of an interface between the silicon melt and the silicon single crystal, and calculating a position of the surface of the silicon melt based on a center position of the silicon single crystal determined from the image of the bright zone; and
controlling, with a controller, the position of the surface of the silicon melt during the pulling of the silicon single crystal while referring to data of the position of the surface of the silicon melt obtained by the first operation and data of the position of the surface of the silicon melt obtained by the second operation, wherein
in performing the first operation:
transforming contours of the real image and the mirror image of the heat shield obtained by the imaging device to project the contours of the real image and the mirror image to a plane corresponding to a lower end position of the heat shield,
calculating a center position of the projected real image of the heat shield through circular approximation of the contour of the opening of the real image of the heat shield that appears as an elliptic shape,
calculating a center position of the projected mirror image of the heat shield through circular approximation of the contour of the opening of the mirror image of the heat shield, and
measuring the spacing between the real image and the mirror image based on a spacing between the center positions of the projected real image and the projected mirror image of the heat shield.

2. The method of producing the silicon single crystal according to claim 1 , wherein
in performing the first operation:
determining the contours of the real image and the mirror image of the heat shield based on differential data of the real image and the mirror image taken by the imaging device.

3. The method of producing the silicon single crystal according to claim 1 , wherein
in performing the first operation:
selecting a contour from contours of each of the real image and the mirror image obtained by the imaging device such that the selected contour encloses an area of not smaller than a predetermined area, and
calculating the center position of each of the real image and the mirror image of the heat shield using the selected contour.

4. The method of producing the silicon single crystal according to claim 1 , wherein
in performing the first operation:
the imaging device takes an image from an angle such that a deviation between the contour of each of the real image and the mirror image of the heat shield and a circular approximated image of the opening of the heat shield is minimized.

5. The method of producing the silicon single crystal according to claim 1 , wherein
in an initial stage of pulling a silicon single crystal, the first operation performs:
performing setting of the position of the surface of the silicon melt based on the spacing between the real image and the mirror image of the heat shield,

from an end on the initial stage to a stage where a diameter of the silicon single crystal reaches a predetermined value, the first operation performs:
controlling the position of the surface of the silicon melt through the controller based on the spacing between the real image and the mirror image of the heat shield, and

in a stage after the diameter of the silicon single crystal reaches the predetermined value, the second operation performs:
controlling the position of the surface of the silicon melt through the controller based on the center position of the silicon single crystal determined from the image of the bright zone.

6. The method of producing the silicon single crystal according to claim 1 , further comprising:
calibrating a difference between the position of the surface of the silicon melt determined in the first operation and the position of the surface of the silicon melt determined in the second operation when the diameter of the silicon single crystal reaches a predetermined value.

Assignees

• Sumco Corp

Inventors

• Takanashi Keiichi
• Hamada Ken

Classifications

• C30B15/26 Primary

  using television detectors; using photo or X-ray detectors · CPC title

• Y10T117/1008

  with responsive control means · CPC title

• C30B29/06

  Silicon · CPC title