Method for measuring distance between lower end surface of heat insulating member and surface of raw material melt and method for controlling thereof

Abstract

A method for measuring a distance between a lower end surface of a heat insulating member and a surface of a raw material melt with a reference reflector provided at a lower end of the heat insulating member which is located above the surface of the raw material melt when a silicon single crystal is pulled up by a Czochralski method while a magnetic field is applied to the raw material melt in a crucible is disclosed. The method comprises the steps of contacting a projection made of quartz, silicon or carbon with the surface of the raw material melt, the projection being longer that the reference reflector and having a length corresponding to an initial distance; electrically detecting the contact between the projection and the melt surface, and observing an initial location of a mirror image of the reference reflector by a camera when the distance between the lower end surface of the heat insulating member and the surface of the raw material melt has been adjusted so as to be the initial distance, the mirror image being reflected on the surface of the raw material melt; and while pulling the silicon single crystal, measuring a travel distance of the mirror image from the initial location by the camera and calculating the distance between the lower end surface of the heat insulating member and the surface of the raw material melt from the initial travel distance of the mirror image.