Apparatus for rotating a crucible of a crystal pulling machine

Single-crystal – oriented-crystal – and epitaxy growth processes; – Apparatus – With means for measuring – testing – or sensing

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117 18, 117208, C30B 3500

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active

055934986

ABSTRACT:
Apparatus and methods for pulling a semiconductor crystal according to a Czochralski method are disclosed. The apparatus includes a crucible containing a melt, a crystal pulling mechanism which pulls the semiconductor crystal from the melt, a motor coupled to the crucible, and a control circuit for energizing the motor to rotate the crucible at a variable speed. The control circuit may energize the motor to rotate the crucible at a continuously varying acceleration and continuously varying rotational speed while the crystal pulling mechanism is pulling at least a portion of the semiconductor crystal from the melt in the crucible. The control circuit may also energize the motor to rotate the crucible at a rotational speed which monotonically increases and decreases. A method for pulling a semiconductor crystal is also disclosed which includes the steps of performing a Fourier analysis on a periodic signal for variably rotating a crucible; generating a sine wave which corresponds to a fundamental Fourier frequency of the periodic signal; and energizing the crucible motor to rotate the crucible at a rotational speed which increases and decreases as a function of the generated sine wave. Other apparatus and methods for pulling crystals with the CZ method to achieve a desired oxygen concentration and gradient are also disclosed.

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H. J. Scheel et al., "Flux Growth of Large Crystals By Accelerated Crucible-Rotation Technique", Journal of Crystal Growth 8 (1971) pp. 304-306.
H. J. Scheel et al., "Crystal Pulling Using ACRT", Journal of Crystal Growth 49 (1980) pp. 291-296.
V. M. Masalov et al., "Hydodynamics and Oscillation of Temperature in Single Crystal Growth From High-Temperature Solutions With Use of ACRT", Journal of Crystal Growth 119 (1992) pp. 297-302.
Leybold-Heraeus GmbH, "Operating Instructions-Crystal Growth Furnace EKZ 2700 GV/CP/C/Si Cable Puller (with Microprocessor)", (pre-1994).

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