The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 01, 1998
Filed:
Apr. 01, 1997
Masao Saitoh, Tokyo, JP;
Daisuke Wakabayashi, Tokyo, JP;
Takashi Atami, Tokyo, JP;
Hisashi Furuya, Tokyo, JP;
Mitsubishi Materials Silicon Corporation, Tokyo, JP;
Mitsubishi Materials Corporation, Tokyo, JP;
Abstract
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.