Leon A Allen

US Patent:

58141480, Sep 29, 1998

Filed:

Feb 1, 1996

Appl. No.:

8/595075

Inventors:

Leon A. Allen - Grover MO

Assignee:

MEMC Electronic Materials, Inc. - St. Peters MO

International Classification:

C30B 1514

US Classification:

117 13

Abstract:

A process for preparing a molten silicon melt from polycrystalline silicon for use in producing single crystal silicon by the Czochralski method is disclosed. Granular and chunk polycrystalline silicon are loaded into a Czochralski crucible as a mixed charge. Preferably, the granular polycrystalline silicon is loaded onto the bottom, mounded toward the centerline of the crucible, and not contacting the upper portion of the wall of the crucible. The chunk polycrystalline silicon is loaded onto the granular polycrystalline silicon. The granular polycrystalline silicon and chunk polycrystalline silicon are melted to form a silicon melt, preferably by heating the polycrystalline silicon from the bottom up such that a substantial portion of the granular polycrystalline silicon is melted before a substantial portion of the chunk polycrystalline silicon is melted. As the melting progresses, the chunk polycrystalline silicon exerts a downward force on the granular polycrystalline silicon to keep the latter in the relatively hotter bottom region of the crucible. If the polycrystalline silicon is exposed to a purge gas, the chunk polycrystalline silicon thermally shields the granular polycrystalline silicon from the cooling effects of the purge gas.

US Patent:

59762470, Nov 2, 1999

Filed:

Jun 14, 1995

Appl. No.:

8/490465

Inventors:

Richard L. Hansen - Cleveland OH
Larry E. Drafall - St. Charles MO
Robert M. McCutchan - St. Louis MO
John D. Holder - St. Louis MO
Leon A. Allen - Grover MO
Robert D. Shelley - Chesterland OH

Assignee:

MEMC Electronic Materials, Inc. - St. Peters MO

International Classification:

C30B 3500

US Classification:

117200

Abstract:

A crucible in which a semiconductor material is melted and held during a crystal growing process. The crucible includes a body of vitreous silica having a bottom wall and a sidewall formation extending up from the bottom wall and defining a cavity for holding the molten semiconductor material. The sidewall formation has an inner and an outer surface. A first devitrification promoter on the inner surface of the sidewall formation is distributed such that a first layer of substantially devitrified silica is formed on the inner surface of the crucible which is in contact with the molten semiconductor material when the semiconductor material is melted in the crucible during the crystal growing process. A second devitrification promoter on the outer surface of the sidewall formation is distributed such that a second layer of substantially devitrified silica is formed on the outer surface of the crucible when the semiconductor material is melted in the crucible during the crystal growing process. The first substantially devitrified silica layer is such that it promotes uniform dissolution of the inner surface and in so doing significantly reduces the release of crystalline silica particulates into the molten semiconductor material as a crystal is pulled from the molten semiconductor material.

US Patent:

59806290, Nov 9, 1999

Filed:

Jun 14, 1995

Appl. No.:

8/490473

Inventors:

Richard L. Hansen - Cleveland OH
Larry E. Drafall - St. Charles MO
Robert M. McCutchan - Lake St. Louis MO
John D. Holder - Lake St. Louis MO
Leon A. Allen - Grover MO
Robert D. Shelley - Chesterland OH

Assignee:

MEMC Electronic Materials, Inc. - St. Peters MO

International Classification:

C30B 1520

US Classification:

117 13

Abstract:

A method of reinforcing a crucible for the containment of molten semiconductor material in a Czochralski process, and of inhibiting formation of dislocations within a single crystal grown by the process. The crucible includes a body of vitreous silica having a bottom wall and a sidewall formation extending up from the bottom wall and defining a cavity for holding the molten semiconductor material. The sidewall formation and bottom wall each have an inner and an outer surface. A first devitrification promoter is deposited on the inner surface of the sidewall formation at a temperature below about 600. degree. C. The deposit is such that, when the crucible is heated above 600. degree. C. , a first layer of substantially devitrified silica forms on the inner surface which is capable of promoting substantially uniform dissolution of the inner surface and reducing the release of crystalline silica particulates into the molten semiconductor material as a crystal is pulled from the molten semiconductor material. A second devitrification promoter is deposited on the outer surface of the sidewall formation at a temperature below about 600. degree. C.