Production process of single crystals

Details Production process of single crystals Production process of single crystals

1990-08-10

1992-12-01

Chaudhuri, Olik

Adhesive bonding and miscellaneous chemical manufacture

Delaminating processes adapted for specified product

Delaminating in preparation for post processing recycling step

1566161, 1566164, 15661641, 156623R, 156623Q, 156DIG83, 422248, C30B 700

Patent

active

051677598

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a process for producing a single crystal from a melt by solidification and crystal growth.
2. Background Art
In view of the recent development of the electronic industry and the like, crystal growing technology has become an extremely important industrial consideration. As materials for new functional devices, compound materials such as GaAs, CdS and ZnSe have now been increasingly recognized to be important in addition to single elemental materials such as Si and Ge. For the production of single crystals from these materials, there is a process in which these single crystals are produced from their corresponding melts by solidification. This process permits formation of large crystals rather easily, so that it is widely used for the growth of single crystals.
The above process is however accompanied by the drawbacks that when the vapor pressure of the melt of a compound is high, an undesirable high amount of the compound evaporates from the crucible and easy formation of a crystal is prevented and when one component of a compound has a higher evaporate rate, the composition of a melt deviates from the stoichiometric composition to result not only in a failure in performing the growth of a crystal as desired but also in the formation of a crystal of reduced quality.
To avoid these problems, quartz ampoules are generally used. Softening of a quartz ampoule however begins at about 1,200.degree. C., beyond which the quartz ampoule may be deformed or may lose transparency and, in the worst case, may explode. Application of the process in which a quartz ampoule is employed is therefore limited to compounds whose melting points are as low as 1,400.degree. C. even at peak temperature.
In the case of a high-melting-point compound having a melting point of 1,400.degree. C. or higher, it has heretofore been the practice that the compound is charged in a crucible of graphite or the like, the crucible is placed in a high-pressure vessel, the vessel is pressurized with an inert gas such as argon, and a crystal is then allowed to grow while the compound is prevented from evaporation, in other words, the high-pressure fusing technique has been conducted to date.
Although the crucible is enclosed within the high-pressure vessel in the above technique, the crucible itself is not closed hermetically and the high-pressure vessel has a large empty space even after the insertion of the crucible therein. Therefore, it is practically impossible to avoid evaporation of a melt and/or deviation from the stoichiometric composition. The above technique is also accompanied by the drawbacks that materials of the high-pressure vessel and heater are corroded and the resulting crystal is contaminated by these materials. In the case of a compound whose melting point is at least 1,400.degree. C., one may consider charging a starting material in a crucible of a high-melting-point metal and after fusion and hermetic enclosure, heating the crucible to conduct growth of a crystal. This process is however accompanied by the drawbacks that the resulting crystal cannot be easily taken from the crucible in many instances, the metal of the crucible may be corroded at portions brought into contact with the melt and the resulting crystal may be contaminated with the metal of the crucible. This process is therefore unsuited for actual practice.
As a method for overcoming these drawbacks, the present inventors found to use a double-walled crucible composed, as shown in FIG. 2, of an outer cylinder 1 made of a material selected from high-melting-point metals and alloys and an inner cylinder 4 made of at least one material selected from high-melting-point metals and alloys, high-melting-point ceramic materials and carbon materials such as graphite. Based on the finding, a patent application has already been filed (Japanese Patent Laid-Open No. 310786/1988). The process which uses the double-walled crucible has the following merits.
(1) A substance having a high melting point and a high vapor

REFERENCES:
patent: 1986196 (1935-01-01), Grosse
patent: 2547521 (1951-04-01), Buehler et al.
patent: 3033659 (1962-05-01), Fischer
patent: 4083748 (1978-04-01), Gault
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patent: 4521272 (1985-06-01), Gault
patent: 4529027 (1985-07-01), Brice et al.
patent: 4612082 (1986-09-01), Westphal et al.
"Growing Quartz Crystals;" A. C. Walker; Electronics, pp. 96-99.
"Growing Single Crystals of High Melting, Decomposable Compounds", Blum et al; IBM Technical Disclosure Bulletin; pp. 1674-1676 vol. 9 No. 12 May 1967.
Patent Abstracts of Japan, vol. 8, No. 93, Apr. 27, 1984 & JP-A-59-8690.
Patent Abstracts of Japan, vol. 13, No. 21, Jan. 18, 1989 and JP-A-225595.
Fischer, "Techniques for Melt-Growth of Luminescent Semiconductor Crystals under Pressure," pp. 41c-47c, J. of Electrochemical Soc. (Feb. 1970).

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