Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from liquid or supercritical state – Having pulling during growth
Reexamination Certificate
2000-03-07
2001-05-29
Hiteshew, Felisa (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from liquid or supercritical state
Having pulling during growth
C117S014000, C117S217000, C117S218000
Reexamination Certificate
active
06238477
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process and to a device for the production of a single crystal of semiconductor material by pulling the single crystal from a melt, which is contained in a crucible and is heated by a side heater surrounding the crucible.
2. The Prior Art
This process for producing single crystals is referred to as the Czochralski method. It is already known that the incidence of specific types of defects in single crystals which are grown depends on the pull rate V and the axial temperature gradient G at the phase boundary between the single crystal and the melt. If the conditions during the pulling of the single crystal are such that the condition V/G<C
crit
is satisfied, C
crit
being a constant, then a majority of interstitial defects, known as large pits, are formed (E. Dornberger,
W. v. Ammon in Electrochemical Society
, Vol. 143, No. 5 (1996)). This type of defect, referred to below as L-defects, can greatly reduce the yield of functional electronic components which are produced by further processing the single crystal. The condition indicated above makes it clear that, in order to avoid the occurrence of L defects, attempts should be made to keep the pull rates as high as possible.
However, when pulling a single crystal, it is found that the pull rate can only be increased up to a certain degree without unacceptably altering the way in which the single crystal grows. Specifically, at excessive growth rates, the single crystal starts to lose the desired cylindrical growth and starts to grow in an imperfectly round shape. Thus instead of forming a cylindrical lateral surface, the single crystal starts to form plane crystal faces corresponding to its crystallographic orientation. Further, growth which is not perfectly round increases the risk of producing crystal lattice defects in the pulled material which renders it unusable.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for delaying the transition from cylindrical growth to growth which is not perfectly round until higher growth rates are reached than were hitherto known.
This object is achieved by the present invention which relates to a process for the production of a single crystal of semiconductor material by pulling the single crystal from a melt, which is contained in a crucible and is heated by a side heater surrounding the crucible, wherein the melt is additionally heated, in an annular region around the single crystal, by an annular heating device or means which surrounds the single crystal and is positioned above the melt.
The process of the invention increases the availability of cylindrically shaped single crystals which are substantially free from L-defects. It is particularly advantageous to use this process for the production of silicon single crystals with large diameters, for example with diameters of 200 mm, 300 mm or 400 mm.
The present invention is also directed to a device for carrying out the process of the invention, wherein an annular heating device which surrounds the single crystal, is positioned above the melt and emits radiation which heats the melt in an annular region around the single crystal.
The annular heating device or means is advantageously positioned above the melt in such a way that the distance between the single crystal and the heating device is less than the distance between the heating device and the wall of the crucible. It is particularly preferable if the distance between the annular heating device and the single crystal is as small as possible, and measures for example only 3 cm.
In another embodiment, it is further preferable if the heating device or means is fastened to the lower edge of a thermally insulating heat shield which screens the single crystal against heat radiation from the side heater. Care should be taken that the heating device heats only the melt, and not the single crystal. Where appropriate, therefore, thermal insulation, for example the heat shield, should be provided between the single crystal and the heating device. The distance between the annular heating device and the surface of the melt is preferably from 10 to 20 mm.
The annular heating device heats the melt in an adjacent surface region lying around the single crystal. It therefore produces a steep axial temperature gradient in the melt, between the single crystal and the crucible. This promotes cylindrical growth of the single crystal.
In a further embodiment, the annular heating device or means may be used to deliver part of the energy needed to produce the melt, and to reduce the time necessary to melt the semiconductor material.
In another embodiment, the heating power of the side heater and, where appropriate, a bottom heater, which is positioned under the crucible, is reduced when the melt is additionally heated by the annular heating device or means. Hence it is possible for the material of the crucible, which usually consists of quartz glass and is attacked by the hot melt, to be protected from premature corrosion. The reduced corrosion rate of the crucible has a favorable effect on the yield of monocrystalline semiconductor material.
In a further embodiment, due to its low thermal inertia, the annular heating device or means can preferably be used for rapid power control. This in turn influences the diameter growth and the pull rate. Therefore, fluctuations in diameter and pull rate can be reduced considerably.
REFERENCES:
patent: 2852420 (1958-09-01), Pohl
patent: 4597949 (1986-07-01), Jasinski et al.
patent: 5132091 (1992-07-01), Azad
patent: 5137699 (1992-08-01), Azod
patent: 5152867 (1992-10-01), Kitaura et al.
patent: 5260037 (1993-11-01), Kitaura et al.
patent: 5441014 (1995-08-01), Tomioka et al.
patent: 5853480 (1998-12-01), Kubota et al.
patent: 5972106 (1999-10-01), Ohta et al.
patent: 198 06 045 (1998-08-01), None
patent: 0811707 (1997-12-01), None
patent: 0866150 (1998-09-01), None
patent: 1316 707 (1963-04-01), None
patent: WO 92/18672 (1992-10-01), None
E. Dornberger, W. von Ammon in Electrochemical Society, vol. 143, No. 5 (1996).
English Patent Abstract of Japan corresponding to JP 60027684.
Patent Abstracts of Japan, vol. 018, No. 244, May 10, 1994, & JP 06027684 (Tokyo Awrakogyo Co. Ltd.), Feb. 4, 1994.
Patent Abstracts of Japan, vol. 7, No. 118, May 21, 1983, & JP 58 036998 (Toshiba Ceramics Co., Mar. 4, 1953.
Patent Abstracts of Japan, vol. 018, No. 575, Nov. 4, '94, & JP 0621591 (Nippon Steel Co.&piotners. 01) Aug. 2, 1994.
Ammon Wilfried Von
Tomzig Erich
Virbulis Janis
Collard & Roe P.C.
Hiteshew Felisa
Wacker Siltronic Gesellschaft fur Halbleitermaterialien AG
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