Method for the production of dislocation-free monocrystalline silicon by floating zone melting

Claim 1

A PROCESS FOR PRODUCING DISLOCATION-FREE MONOCRYSTALLINE SILICON BY CRUCIBLE-FREE ZONE MELTING WHICH COMPRISES: (A) VERTICALLY MOUNTING A SILICON ROD BY ONE END; (B) MOUNTING A MONOCRYSTALLINE SEED CRYSTAL IN VERTICAL ALIGNMENT WITH SAID SILICON ROD; (C) ATTACHING SAID SEED CRYSTAL TO THE UNATTACHED END OF SAID SILICON ROD, SAID SEED CRYSTAL HAVING A SMALLER DIAMETER THAN SAID SILICON ROD; (D) INITIATING A ZONE-MELTING PASS IN SAID SEED AND CONTINUING SAID ZONE-MELTING PASS TO THE OPPOSITE END OF SAID ATTACHED SILICON ROD; (E) REPEATING STEP (D) SEVERAL TIMES: (F) COMMENCING THE LAST REPETITION OF STEP (D) IN THE SEED CRYSTAL AT A RATE BETWEEN 7 AND 15 MM. PER MINUTE; (G) AS THE MOLTEN ZONE OF STEP (F) MOVES THROUGH THE JUNCTION OF SAID SEED CRYSTAL AND SAID SILICON ROD, MOVING THE END OF SAID SEED CRYSTAL AND SAID SILICON ROD AXIALLY APART AT A RATE ABOVE 25 MM. PER MINUTE, TO PRODUCE A CONTRACTED CROSS SECTION OF ABOUT 2 MM.; (H) AND REDUCING THE RATE OF THE MOLTEN ZONE PASS, AS IT TRAVELS FROM SAID CONTRACTED CROSS SECTION OF STEP (G) TO THE FULL CROSS SECTION OF SAID SILICON ROD, TO A VALUE LESS THAN 7 MMM. PER MINUTE.