Patent ID: 6454851
Filing Date: 2002-09-24
Classification: C30B

Abstract:
A method for preparing molten silicon melt from polycrystalline silicon in a crystal pulling apparatus, the method comprising:loading polycrystalline silicon into a crucible, the amount of polycrystalline silicon loaded into the crucible being substantially less than a total amount of polycrystalline silicon to be melted in the crucible; heating the crucible to melt down the polycrystalline silicon in the crucible to form a partially melted charge in the crucible, the partially melted charge comprising molten silicon having an upper surface and an island of unmelted polycrystalline silicon exposed above thee upper surface of the molten silicon; selectively feeding granular-polycrystalline silicon from a feeder onto the island of unmelted polycrystalline silicon in the crucible at a feed rate until the total amount of polycrystalline silicon has been loaded into the crucible; determining electronically the position of the island of unmelted polycrystalline silicon relative to the side wall of the crucible, said determining step being conducted as granular-polycrystalline silicon is fed onto the island of unmelted polycrystalline silicon in the crucible; and controlling the feed rate at which granular-polycrystalline silicon is fed from the feeder onto the island of unmelted polycrystalline silicon in response to the determined position of the island of unmelted polycrystalline silicon relative to the crucible side wall at the upper surface of the molten silicon.