Single-crystal – oriented-crystal – and epitaxy growth processes; – Apparatus – For crystallization from liquid or supercritical state
Patent
1993-12-22
1995-08-15
Breneman, R. Bruce
Single-crystal, oriented-crystal, and epitaxy growth processes;
Apparatus
For crystallization from liquid or supercritical state
117 31, 117208, C30B 3500
Patent
active
054410142
DESCRIPTION:
BRIEF SUMMARY
INDUSTRIAL FIELD OF THE INVENTION
This invention relates to an apparatus for pulling up a single crystal according to Czochralski method, and more particularly to an apparatus for pulling up a single crystal, which is provided with screens which can float up a single crystal at a high speed while controlling contamination of the crystal, which is caused by impurities, and without impeding the single crystallization.
PRIOR ART
As known apparatus for pulling up a single crystal, in which the pulling-up speed of the crystal is improved, there are some patent applications. Japanese Patent Kokai No. 62-138386 discloses a technique of speeding up the floating rate while controlling contamination of the crystal, by shielding the radiant heat generated from the melt with the provision of a radiant screen of an approximately inverted cone-shaped, heat-insulating multilayer structure thereby to prevent the pulling-up single Crystal from heating, said multilayer structure being provided close to the surface of the melt and its surface being sintered with a ceramic body or ceramic-coated.
Alternately, Japanese Patent Kokai No. 63-256593 discloses a technique of aiming at a further effect for speeding up the pulling by providing a shielding member of upturned trapezoid shape in section, which member surrounds the pulling-up zone of the single crystal, and a cooling mechanism.
Alternately, as a technique of improving the pulling-up rate of the single crystal and the non-transition of the crystal, which is caused by contamination of impurities, Japanese Patent Kokai No. 63-50391 discloses the one wherein a cylinder is provided in the periphery of a growing single crystal, said cylinder having a cooling mechanism in its periphery, the inner peripheral surface of the cylinder forming a reflection surface of radiant heat, and the surface said cylinder opposing the melt material forming a reflection surface of the radiant heat. Further, as a technique of removing contamination caused by impurities Japanese Patent Kokai No. 64-18988 describes the one of disposing a plurality of heat shielding plates made concentrically of metal or graphite, in the periphery of the pulled-up single crystal, in such a way that they may communicate with the outside without enclosing the crucible while keeping spaces mutually. Furthermore, as a technique of improving the pulling-up rate of the single crystal and the non-trasition caused by contamination of impurities, Patent Kokai No. 1-145391 describes the one of providing, in a cooling means arranged at the circumference of the pulled-up single crystal, a shielding element made of molybdenum to shield the space between said cooling means and the crucible or the melt in the crucible.
However, such known techniques have the following disadvantages.
(1) To speed up the pulling rate of a growing crystal it is important to have the transmitted heat from the melt, the latent heat for solidification in the crystallization process, the radiant heat emitted from heat source such as the melt or heater, and the like, escapted quickly from the growing crystal. Particularly, it is possible to speed up the pulling-up ate if the temperature gradient near the interface of the solid solution is great, even if the consequentinal temperature gradient in the growing crystal were small i.e. the cooling rate were a little bit slow.
However, in the techniques such as inverted cone-shaped screen, which are disclosed in the conventional apparatus, the view angle to the growing crystal is sufficiently small particularly in the neighborhood of the solid solution interface, so that the radiant heat or the like generated from the neighborhood of said
Alternately, Japanese Patent Kokai No. 63-256593 discloses a technique of aiming at a further effect for speeding up the pulling by providing a shielding member of upturned trapezoid shape in section, which member surrounds the pulling-up zone of the single crystal, and a cooling mechanism.
Alternately, as a technique of improving the pulling-up rate of the single crystal
REFERENCES:
patent: 3694165 (1972-09-01), Kramer
patent: 4956153 (1990-09-01), Yamashita et al.
patent: 4981549 (1991-01-01), Yamashita et al.
patent: 5264189 (1993-11-01), Yamashita et al.
patent: 5316742 (1994-05-01), Tomioka et al.
Matsuzaki Akihiro
Nagai Kazunori
Tomioka Junsuke
Breneman R. Bruce
Garrett Felisa
Komatsu Electronic Metals Co. Ltd.
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