Silicon single crystal manufacturing apparatus and silicon single crystal manufacturing method

摘要

The distance between the heat shield and the melt level of the melt can be regulated in a high precision. The real image includes at least the circular opening of the heat shield provided in such a way that the heat shield covers a part of the melt level of the silicon melt. The mirror image is a reflected image of the heat shield on the surface of the silicon melt. Based on the distance between the obtained real image and the mirror image, the melt level position of the silicon melt is computed, and the distance between the heat shield and the melt level position is regulated.

主权项

1. A silicon single crystal manufacturing apparatus for pulling the silicon single crystal from a silicon melt stored in a crucible comprising:
an imaging device that takes an image of an area including a melt level of the silicon melt from a location above the melt level of the silicon melt in a direction tilted with respect to a silicon single crystal pulling axis in a predetermined angle; a heat shield that is provided in such a way that the heat shield covers a space above and extends parallel to the melt level of the silicon melt with a separation from the melt level of the silicon melt, a circular opening, which the silicon single crystal penetrates during pulling the silicon single crystal, being provided to the heat shield; and a calculator that takes a real image of the heat shield including at least the opening part and a mirror image of the heat shield reflected on a surface of the silicon melt, calculates an interval between the real image and the mirror image, and converts the interval to a melt level position of the silicon melt, wherein the calculator is configured to correct distorted real and mirror images of the opening of the heat shield into undistorted plan view images by mapping transformation, in which a point on an imaging element of the imaging device is projected on an xy plane corresponding to a lower end plane of the heat shield by using formulas (1) to (3) below:xp=-au⁢uyp=yc-av⁢v⁢⁢cos⁢⁢θczp=zc+av⁢v⁢⁢sin⁢⁢θc}(1)yc=yf2+zf2⁡[1+fl/(yf2+zf2-fl)]⁢sin⁢⁢θczc=yf2+zf2⁡[1+fl/(yf2+zf2-fl)]⁢cos⁢⁢θc}(2)X=-xp⁢zf⁢/⁢(zp-zf)Y=(yf⁢zp-yp⁢zf)⁢/⁢(zp-zf)}(3) wherein: x, y, and z are numerical coordinates of a three-dimensional space, an origin of the coordinate is an intersection between a straight line drawn from a center of the imaging element and the xy plane, the straight line passing through a center of lens of the imaging device, silicon single crystal ingot pulling direction is in a z axis in a positive direction, the center of the imaging element and the center of the lens are in a yz plane, a coordinate (u, v) on the imaging element are obtained by pixels on the imaging device and corresponds to a point (xp, yp, zp) on the imaging device by using the formula (1) above, αu and αv are a horizontal and vertical size of the imaging element of the imaging device, yc and zc are the y-coordinate and z-coordinate of the center of the imaging device, θc is defined as an angle between the z axis and the straight line, the coordinate (0, yc zc) is obtained by the formula (2) above using coordinates of the center of the lens (0, yf, zf), f1 being a focal point distance of the lens used, and a coordinate (X, Y, Z) on the xy plane is obtained by the formula (3) above in a case where the point (xp, xy, xz) on the imaging element is projected on the xy plane through a coordinate of the center of the lens (0, yf zf) by regarding the lens as a pinhole; and by regarding the projected point as (X, Y, 0).