Patent ID: 6171391
Filing Date: 2001-01-09
Classification: C30B,Y10T

Abstract:
A method for use in combination with an apparatus for growing a silicon single crystal, said crystal growing apparatus having a heated crucible containing a silicon melt from which the single crystal is pulled, said crystal growth apparatus also having a reflector positioned within the crucible above the melt, said reflector having an inner surface defining a central opening through which the crystal is pulled, said melt having a top surface on which a reflection of the reflector is visible, said crystal being pulled generally along a central axis that is substantially perpendicular to the top surface of the melt, said method comprising the steps of:generating images of a portion of the reflector and a portion of the reflection of the reflector on the top surface of the melt with a camera, said images each including a plurality of pixels, said pixels each having a value representative of an optical characteristic of the image;processing the images as a function of the pixel values to detect at least two edges of the reflector and at least two edges of the reflection in the images, said edges of the reflection corresponding to a virtual image of the reflector;measuring the distance between the detected edges of the reflector to determine a dimension of the reflector in pixels and measuring the distance between the detected edges of the reflection to determine a dimension of the virtual image of the reflector in pixels;determining a distance from the camera to the reflector and a distance from the camera to the virtual image of the reflector based on the relative positions of the detected edges in the images;determining at least one parameter representative of a condition of the crystal growing apparatus based on the determined distances; andcontrolling the crystal growing apparatus in response to the determined parameter.