Crucible-free zone melting method and apparatus for producing and processing a rod-shaped body of crystalline substance, particularly semiconductor substance

Claim 1

A CRUCIBLE-FREE ZONE MELTING PROCESS FOR TREATING A SEMICONDUCTOR MATERIAL, COMPRISING SUPPORTING A ROD OF SAID MATERIAL VERTICALLY, MELTING A LENGTHWISE LIMITED ZONE OF SAID ROD BY HIGH FREQUENCY ELECTROMAGNETIC INDUCTION, THE MOLTEN ZONE FORMING AN ELECTRIC CONDUCTOR IN THE HIGH FREQUENCY FIELD, WHICH FIELD IS OF LIMITED LENGTHWISE EXTENT, CARRYING OUT A MELTING-ZONE PASS OPERATION BY RELATIVELY DISPLACING THE HIGH FREQUENCY FIELD WITH RESPECT TO THE ROD IN ITS LONGITUDINAL DIRECTION, TO CAUSE THE MOLTEN ZONE TO TRAVEL ALONG THE ROD, THE MATERIAL OF THE TRAVELLING MOLTEN ZONE BEING HEATED IN AT LEAST MAJOR PART BY ELECTRIC CURRENT INDUCTIVELY GENERATED WITHIN THE ROD, THE MELTING OPERATION BEING INITIATED BY PREHEATING BY HEAT TRANSFER FROM AN AUXILIARY HEATING MEANS, THE PREHEATING BEING AT A LOCATION RELATIVELY SMALL WITH RESPECT TO THE LONGITUDINAL EXTENT OF THE MELTING ZONE PASS, A MONOCRYSTALLINE SEED BEING FUSED INTO AN END REGION OF THE ROD SPACED LENGTHWISE OF THE LOCATION OF PREHEATING, THE HIGH FREQUENCY ELECTRIC FIELD BEING JUXTAPOSED WITH RESPECT TO SAID SMALL LOCATION AND THE SUPPLIED ELECTRIC POWER BEING LIMITED TO EFFECT INDUCTIVE HEATING OF THE ROD SUFFICIENT TO PROVIDE A ZONE OF GOOD ELECTRIC CONDUCTIVITY OF THE ROD BUT NOT SUFFICIENT TO MELT THE ROD, AND DISPLACING SAID HIGH FREQUENCY FIELD AND SAID ZONE, WHICH IS SOLID, WITH RESPECT TO AND THROUGH THE ROD IN A DIRECTION AWAY FROM SAID LOCATION OF PREHEATING WHILST THE AUXILIARY HEATING MEANS STOPS OPERATING, THEREAFTER INCREASING THE ELECTRIC POWER TO MELT A ZONE OF THE ROD AND DISPLACING THE HIGH FREQUENCY FIELD, AND CONSEQUENTLY THE MOLTEN ZONE, ALONG THE ROD IN THE OPPOSITE DIRECTION, THE SEEDED END REGION OF THE ROD BEING ROTATED ABOUT THE LONGITUDINAL AXIS OF THE ROD DURING THE MELTING-ZONE PASS OPERATION, THE OPPOSITE END NOT BEING ROTATED DURING SAID PASS OPERATION.