Mitsubishi Materials Corporation

Mitsubishi Materials Silicon Corporation

Masao Saitoh

Daisuke Wakabayashi

Hisashi Furuya

Takashi Atami

Toshio Anbe

The invention is directed to preventing meltdown of conductive metal electrodes 5, 5 used to supply current to a heater 104 of a crucible 103. A single crystal pulling apparatus comprises: the heater 104 which encircles the crucible 103, and the pair of electrodes 5, 5, respectively threaded to a pair of graphite intermediate electrodes 6 of the heater 104, and a voltage source 9 for supplying power to the pair of electrodes 5, 5. A switch 11 switches the power on and off. A watthour meter 10a, continuously measures the current flowing through the heater 104. Investigation by the present inventors showed that in the case of a crack 8 in a lower portion of the intermediate electrode 6, minute fluctuations occurred in the measured value of the current, arising from an electric discharge phenomena in the crack 8 prior to meltdown of the electrodes 5, 5. Therefore, if fluctuations in the electric current measured by the wattmeter 10a are outside of a tolerance range, the controller 12 switches off the switch 11, thus interrupting power to the electrodes 5, 5, and preventing meltdown of the electrodes 5, 5.

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Tokyo, Japan

Masao Saitoh