Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from liquid or supercritical state – Having pulling during growth
Patent
1997-05-21
1999-03-23
Hiteshew, Felisa
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from liquid or supercritical state
Having pulling during growth
117209, C30B 1534
Patent
active
058853456
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of fabricating a semiconductor monocrystal or multicrystal of a material such as silicon, germanium, or bismuth telluride, and, in particular, to a method of fabricating a semiconductor crystal that is formed to have a predetermined shape.
BACKGROUND OF ART
A method of fabricating a large number of cube-shaped monocrystal pieces with sides on the order of 1 to 3 mm is known in the prior art as a method of fabricating pieces of a semiconductor crystal, such as a monocrystal or multicrystal semiconductor of a bismuth/tellurium compound; which involves slicing an ingot of monocrystal or multicrystal grown in an a-axial direction by a downward-drawing method to form circular plates, then dicing these circular plates.
Other methods, such as Edge-defined Film-fed Growth (EFG) and crosscut methods, are also known in the prior art as methods of fabricating sheets of semiconductor crystal such as silicon ribbon crystals.
However, the above method of fabricating monocrystal or multicrystal semiconductor pieces of a bismuth/tellurium compound necessitates a cutting process of one slicing step and two dicing steps, so it is expensive.
Furthermore, the silicon melt solidifies at a speed of ten to several hundred mm/minute with the above EFG and crosscut methods, so the grain size of the completed crystals is small and thermal stresses still remain therein, and thus quality is poor.
The present invention was devised in the light of the above problems and has as an objective thereof the provision of an inexpensive method of fabricating shaped crystals of a needle shape (diameter: approximately 0.5 mm to 3 mm) or sheet shape (thickness: approximately 0.5 mm) from a high-quality bismuth/tellurium compound or other semiconductor.
DISCLOSURE OF INVENTION
This invention concerns a method of fabricating a shaped crystal by overhead-pressure liquid injection, comprising a step of heating a raw crystal material within a shaping vessel set in a predetermined atmosphere, to form a melt; a step of pressuring the melt from overhead, to inject the same into a shaper disposed within the shaping vessel; and a step of cooling the melt injected into the shaper, to form a crystal.
The melt could be injected inward from above or below the shaper. The pressuring during this time could be performed by a mechanical force or by the use of a gas pressure that is set by means for setting the atmosphere of the shaping vessel.
If the shaping vessel is formed to have a box shape and a plurality of conical holes are provided in the base of the interior thereof for controlling the orientation of crystals, it is possible to control a-axis orientation.
If the shaper is configured of a plurality of plate members, each having grooves of a predetermined shape in the vertical direction and being linked together in such a manner that the grooves are opposing, a large number of needle crystals can be fabricated simultaneously.
If the shaper is configured of a linked series of a plurality of plate members formed to have steps of predetermined dimensions along left and right edges thereof, a plurality of sheet crystals can be fabricated simultaneously.
Since the present invention can thus be used to fabricate a number of shaped crystals simultaneously, fabrication costs are reduced. The speed of growth of the crystals can also be slowed so that high-quality crystals are obtained.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows a first example of the crystal melt injection method in accordance with this invention;
FIG. 2 shows a second example of the crystal melt injection method in accordance with this invention;
FIG. 3 shows a third example of the crystal melt injection method in accordance with this invention;
FIG. 4 shows essential components of a device for fabricating needle monocrystals of a thermoelectric compound semiconductor;
FIG. 5 is a perspective view of the shaping vessel
FIG. 6 is a vertical cross-sectional view of the shaping vessel;
FIG. 7 is a plan view of the shaping vessel;
FIG.
REFERENCES:
patent: 4540550 (1985-09-01), Gaida et al.
patent: 4610754 (1986-09-01), Gaida et al.
"Modeling of high pressure, liquid-encapsulated Czochralski growth of InP crystals"; Zhang, et al.; J. Cryst. Growth (1996), pp. 250-260. (Abstract Only).
Hiteshew Felisa
Union Material Inc.
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