Motorola Corporation

Donald R Clement

Roger G Nikirk

Lawrence D Mason

Carl A Helber

A method for the controlled melting of an end of a polycrystalline semiconductor body. The polycrystalline body is divided into two or more segments and the segments are positioned in a spaced apart relationship so as to be electrically isolated from each other by narrow gaps. One end of the segments is heated by an external heating means such as by induction heating to cause a portion of the end of the segments to melt. Some of the molten material so formed then flows into the gap separating the segments and electrically shorts together the segments. The opposite ends of the segments are connected to an electrical power supply and a heating current is passed through the segments and through the molten material bridging the gaps. Separately adjusting the heating effects of the external heating means and the heating current makes possible the controlled heating and controlled melting of the end portions of the segments.

Method for the controlled melting of semiconductor bodies

Apparatus for automatically controlling, by stationary optical means, the diameter of a crystal from seed to final taper in a Czochralski crystal pulling method is disclosed. The diameter control has a feed back loop including diameter sensing means which controls a motor for moving the pulled crystal up faster or slower. The diameter, at any value, is sensed by two closely adjacent photocells receiving radiation from spaced points on the solid-liquid interface and a voltage value corresponding to that diameter is developed. When a constant diameter is being maintained and the diameter increases, the magnitudes of the sensed radiation change and a difference signal voltage in one direction is generated causing the crystal pull rate to increase. When the diameter decreases the magnitudes of the sensed radiation change in the reverse and a difference signal voltage in the opposite direction is generated causing crystal pull rate to decrease. For causing the crystal to grow in diameter as desired an offset voltage according to a predetermined program is balanced against the photocell voltage error voltage of one pair of photocells and the resultant difference signal is used to control the pull speed so as to change the diameter accordingly. When the diameter has changed, for example, increased to a point where the liquid-solid interface has changed location sufficiently, the next set of photocells takes over to develop an error voltage. A further diameter related offset voltage is developed and balanced against the error voltage and the crystal is forced to continue to increase in diameter accordingly. The process continues until final diameter is reached.

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Scottsdale, AZ, United States of America

Donald R Clement