Method for measuring distance between lower end surface of heat shielding member and surface of raw material melt, method for controlling distance between lower end surface of heat shielding member and surface of raw material melt and method for manufacturing silicon single crystal

A method for measuring a distance between a lower end surface of a heat shielding member and a surface of a raw material melt, the method comprising providing the heat shielding member being located above the surface of the raw material melt, when a silicon single crystal is pulled by the Czochralski method while a magnetic field is applied to the raw material melt in a crucible, the method including:

• forming a through-hole in the lower end surface of the heat shielding member;
• actually measuring the distance between the lower end surface of the heat shielding member and the surface of the raw material melt, and observing a position of a mirror image of the through-hole with an optical camera, the mirror image being an image reflected on the surface of the raw material melt;
• and then
• measuring a moving distance of the mirror image by the optical camera, and calculating the distance between the lower end surface of the heat shielding member and the surface of the raw material melt from a value obtained in the actually measuring and the moving distance of the mirror image, during the pulling of the silicon single crystal,
• wherein while observing position of the mirror image of the through-hole, the through-hole is detected as a dark portion and the portion other than the through-hole is detected as a bright portion in the mirror image of the lower end of the heat shielding member projected on the surface of the raw material melt, and
• wherein the through-hole is surrounded on all sides by the heat shielding member.