Apparatus for pulling rod-shaped crystals of semiconductor material from a melt in acrucible

Claim 1

APPARATUS FOR PULLING ROD-SHAPED CRYSTALS OF SEMICONDUCTOR MATERIAL FROM A MELT IN A CRUCIBLE, COMPRISING A PROCESSING VESSEL; A CRUCIBLE CONTAINING THE MELT POSITIONED IN SAID PROCESSING VESSEL; HEATER MEANS IN OPERATIVE PROXIMITY WITH SAID CRUCIBLE FOR HEATING THE MELT AT A SUBSTANTIALLY CONSTANT TEMPERATURE; CRYSTAL PULLING MEANS MOUNTED IN SAID VESSEL ABOUT SAID CRUCIBLE FOR SUBSTANTIALLY VERTIICAL MOVEMENT, SAID CRYSTAL PULLING MEANS COMPRISING A SUBSTANTIALLY VERTICALLY DISPLACABLE MEMBER, DRIVING MEANS IN OPERATIVE PROXIMITY WITH SAID MEMBER FOR MOVING SAID MEMBER IN A SUBSTANTIALLY VERTICAL DIRECTION AND CRYSTAL HOLDER MEANS ON SAID MEMBER FOR SEEDING AND PULLING A CRYSTAL ROD UPWARDLY OUT OF THE MELT WHEN SAID MEMBER IS MOVED UPWARDLY; STRAIN GAGE MEANS AFFIXED TO THE MEMBER OF SAID CRYSTAL PULLING MEANS FOR PROVIDING AN ELECTRIICAL SIGNAL HAVING A MAGNITUDE INDICATIVE OF THE WEIGHT OF SAID CRYSTAL ROD; CIRCUIT MEANS INCLUDING VARIABLE RESISTANCE MEANS HAVING A RESISTANCE-VARYING ARM MECHANICALLY COUPLED TO THE DRIVING MEANS OF SAID CRYSTAL PULLING MEANS FOR PROVIDING AN ELECTRICAL SIGNAL HAVING A MAGNITUDE INDICATIVE OF THE LENGTH OF SAID CRYSTAL ROD; ELECTRICAL COMPARATOR MEANS INCLUDING SAID STRAIN GAGE MEANS AND SAID CIRCUIT MEANS FOR COMPARING THE ELECTRICAL SIGNALS CORRESPONDING TO THE WEIGHT AND THE LENGTH OF THE CRYSTAL ROD TO PRODUCE AN ELECTRIC CONTROL SIGNAL PROPORTIONAL TO THE DIFFERENTIAL QUOTIENT OF THE RATE OF CHANGE OF WEIGHT TO THE RATE OF CHANGE OF LENGTH OF SAID CRYSTAL ROD; AND CONTROL MEANS CONNECTED TO SAID ELECTRICAL COMPARATOR MEANS AND COUPLED TO THE DRIVING MEANS OF SAID CRYSTAL PULLING MEANS FOR CONTROLLING THE PULLING SPEED BY THE ELECTRIC CONTROL SIGNAL TO MAINTAIN THE DIFFERENTIAL QUOTIENT CONSTANT THEREBY TO MAINTAIN THE DIAMETER OF THE ROD-SHAPED CRYSTAL CONSTANT.