Siemens Aktiengesellschaft

Friedrich Ticak

Hans Stut

Method of crucible-free zone-melting a semiconductor rod which includes monitoring a melting zone formed in and traveling through a semiconductor rod surrounded by an induction heating coil, producing a respective signal corresponding to values of the actual diameters d of the semiconductor rod at a crystallization interface of the melting zone, comparing the signals corresponding to the actual diameter values d with a signal corresponding to a nominal diameter value d.sub.s so as to produce a signal corresponding to a respective first control deviation .DELTA.d, continuously combining the signals corresponding to the actual diameter values d and the signal corresponding to the respective first control deviation .DELTA.d to form respective signals corresponding to a new nominal diameter value d.sub.s *, respectively, in accordance with the relationships:

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Munich, Germany

Friedrich Ticak