Growing semiconductor crystalline materials

Details Growing semiconductor crystalline materials Growing semiconductor crystalline materials

1990-10-12

1994-09-27

Breneman, R. Bruce

Single-crystal, oriented-crystal, and epitaxy growth processes;

Processes of growth from liquid or supercritical state

Having pulling during growth

117 32, 117917, C30B 1520

Patent

active

053499212

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a method and apparatus for growing semiconductor crystalline materials in which a melt of the growing crystal is subjected to a magnetic field.
2. Discussion of Prior Art
Electronic devices are fabricated on wafers of semiconductor crystals. The properties of the semiconductor are heavily dependent on the specific impurities present in the wafers. Not all impurities are deleterious, and successful fabrication of electronic devices requires the control of the distribution and concentration of the impurities. For most electronic devices the starting material comprises a slice of wafer cut from a single crystal of the semiconductor, commonly either silicon or gallium arsenide. The crystal is in turn pulled from a melt. An object of this invention is an improvement to the techniques for the growth of semiconductor crystals which leads to improved homogeneity of certain impurities in the crystal.
Semiconductor crystals are for the most part grown from melts of the semiconductor in a crystal pulling apparatus. To control the electrical properties of the crystals, small quantities of specific impurities or dopants are added to the melt. One of the major problems in the production of crystals is to achieve control over the uniformity and concentration of dopants within the crystal.
During the growth process differences in composition or temperature between differing regions of the melt lead to density variations in the melt which can in turn have undesirable effects on the incorporation of impurities within the growing crystal and lead to the formation of localised fluctuations of impurity concentrations known as striae.


SUMMARY OF THE INVENTION

Often, during crystal growth, the crystal and sometimes other parts of the apparatus are rotated to provide uniformity within the growing crystal. These rotations are also partly responsible for setting up convective flows within the melt. The form of these convective flows greatly affects the quality of the growing crystal and can help to promote uniformity of the crystal. One effect of the rotation of the crystal is to set up a convective motion in the melt ahead of the growing crystal as a result of the centrifugal pumping action of the rotating crystal. Such crystal rotation driven flow is generally desirable as it results in an improved radial uniformity to the crystal.
In recent years much interest has been displayed in the potential for damping of the convective flows in the melt through the application of externally applied magnetic fields. The melts of semiconductors are generally good electrical conductors and it is well established that it is possible to damp the convective flows within the melts by the application of a static magnetic field to the melt. This can lead to greatly differing patterns of incorporation of impurity within the crystal.
To date two geometries have been widely reported. In the so called axial systems a coil is placed co-axially with the rotation axis of the crystal so as to generate a field in the melt predominantly directed parallel to the rotation axis. In some modifications of this method several coils are used, all co-axial with the rotation axis, and with current circulating in the same sense in each coil. The objective of such an arrangement is to provide a much more uniform field over the melt volume. The second geometry is to use a magnet oriented so as to generate a field transverse to the growth direction of the crystal. Such a geometry destroys the rotational symmetry which is generally considered desirable during crystal growth.
While the application of static magnetic fields has been shown to be capable of damping the convective flows within the melt and so reducing the striae, the quality of the crystal may be degraded in other respects. For example in UK Patent GB 2,163,672 A it is proposed that the reduction in heat transport through the melt brought about by the reduced convection can lead to unacceptably high crucible wall temperatures du

REFERENCES:
patent: 4508970 (1985-04-01), Ackerman
patent: 4565671 (1986-01-01), Matsutani et al.
patent: 4592895 (1986-06-01), Matsutani et al.
patent: 4617173 (1986-10-01), Latka
patent: 4705591 (1987-11-01), Carle et al.
patent: 4830703 (1989-05-01), Matsutani
patent: 4849188 (1989-07-01), Takasu et al.
Patent Abstracts of Japan, vol. 9, No. 160 (C-289) (1883), 4 Jul. 1985 & JP, A, 6033296 (Toshiba Ceramics K.K.) 20 Feb. 1985.
Pat. Abstracts of Japan, vol. 9, No. 218 (C-301) (1941), Sep. 5/85; & JP A 6081086 (Shinetsu HJandoutai K.K.) May 9, 1985.
Pat. Abstracts of Japan, vol. 9, No. 160 (C-289) (1883), Jul. 4, 1985, & JP A, 6033287 (Toshiba K.K.), Feb. 20, 1985.
Pat. Abstracts of Japan, vol. 9, No. 160 (C-289) (1883), Jul. 4, 1985, & JP A, 6033298 (Toshiba Ceramics K.K.) 20 Feb. 1985.

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