METHOD FOR DETECTING GAP IN SINGLE CRYSTAL PULLING MACHINE AND DEVICE FOR CONTROLLING THE GAP

摘要

PROBLEM TO BE SOLVED: To stabilize the quality of a single crystal rod and to improve the yield of the rod by controlling a gap to be optimum even when the surface of a melt waves. SOLUTION: Melt 13 is stored in a crucible 14 provided in a chamber 12 and a heated for heating the melt is installed so as to surround the outer peripheral surface of the crucible 14. A heat shielding member 26 surrounding the outer peripheral surface of a single crystal rod 24 pulled from the melt is provided in such a manner that the lower end of the heat shielding member 26 is situated above the surface of the melt so as to leave a gap H, and radiant heat from the heater is interrupted with this heat shielding member 26. A controller 33 controls a lifting device 18a for lifting/ lowering a crucible so that the gap H is kept at a standard value. Coils 27 are attached to the peripheral surface of the heat shielding member 26 in such a manner that the axial line of the coils is directed toward the surface of the melt, and high-frequency current is allowed to flow through the coils by a high frequency electric power source, thereby eddy current is generated at the surface of the melt. A detecting means 29 detects the change in impedance of the coils 27 caused by generation of the eddy current, and the controller 33 controls the lifting device 18a according to the detection output.