Heating – Accessory means for holding – shielding or supporting work... – Crucible
Patent
1997-03-06
1999-03-23
Housel, James C.
Heating
Accessory means for holding, shielding or supporting work...
Crucible
432156, 432263, 428 341, F27B 1410, B29D 2200
Patent
active
058850716
ABSTRACT:
In order to reduce concentrations of impurities in an inner layer of a quartz crucible for pulling a silicon single crystal which comprises an outer layer made of quartz glass and an inner layer formed on the inner surface of the outer layer, a migration-preventing layer is formed between the outer and inner layers, wherein the migration-preventing layer prevents migration of the impurities such as alkaline metals included in the natural quartz glass in the outer layer to the synthetic quartz glass in the inner layer. The method of producing a crucible using a mold with an upper opening comprises the steps of: feeding a first quartz powder into the mold along an inner surface of the mold to pile up the first quartz powder in a layered structure and form a preform of the first quartz powder; melting a part of the preform by heat radiated from inside the preform; cooling the preform to solidify and form a crucible substrate of an opaque quartz glass layer; generating a high temperature gas atmosphere inside the substrate during or after formation of the substrate; feeding a second quartz powder containing aluminum or in combination with an aluminum-containing component into the gas atmosphere and melting it in the gas atmosphere; settling the second quartz powder melt flying from the gas atmosphere on an inner surface of the substrate to form an aluminum-containing intermediate quartz glass layer; feeding a third quartz powder into the gas atmosphere and melting it in the gas atmosphere; and it as settling the third quartz powder melt flying from the gas atmosphere on the inner surface of the aluminum-containing quartz glass layer to form a transparent quartz glass layer with high purity.
REFERENCES:
patent: 4528163 (1985-07-01), Albrecht
patent: 4956208 (1990-09-01), Uchikawa et al.
patent: 5174801 (1992-12-01), Matsumura et al.
K. Katsuhiko. Quartz glass crucible and its production. Publication No. 08-002932, Abstract, 09 Jan. 1996.
Sato Tatsuhiro
Watanabe Hiroyuki
Devi S.
Housel James C.
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