Patent ID: 8361223

Claim:
A method for measuring a liquid level in a single crystal pulling apparatus employing a CZ method, in which, in a CZ furnace provided with a heat shield surrounding a periphery of a single crystal to be pulled up out of a raw material melt held in a crucible and having a rim at a lower end thereof, a laser beam emitted by a laser beam source is projected onto a melt surface, the laser beam reflected on the melt surface is received, and the liquid level of the melt surface is measured based on the principle of triangulation, the method comprising: setting a plurality of measuring methods having different ways of determining the liquid level; acquiring, prior to manufacturing, information that associates any of the plurality of measuring methods to each gap from a predetermined position, set between an outer peripheral face of the single crystal and the heat shield, up to the outer peripheral face of the single crystal; carrying out an actual measurement of the gap during the pulling and growth of the single crystal; selecting a measuring method associated to the gap obtained by the actual measurement, on the basis of the information; and measuring the liquid level of the melt surface in use of a selected reflection method.