APPARATUS AND METHOD FOR ROTATING CRUCIBLE OF CRYSTAL PULLING MACHINE

摘要

Apparatus and method for pulling a semiconductor crystal according to a Czochralski method are disclosed. The apparatus includes a crucible (34) containing a melt (M), a crystal pulling mechanism (26,28) which pulls the semiconductor crystal (58) from the melt (M), a motor (40) coupled to the crucible (34), and a control circuit (46) for energizing the motor (40) to rotate the crucible (34) at a variable speed. The control circuit (46) may energize the motor (40) to rotate the crucible (34) at a continuously varying acceleration and continuously varying rotational speed while the crystal pulling mechanism (26,28) is pulling at least a portion of the semiconductor crystal (58) from the melt (M) in the crucible (34). The control circuit (46) may also energize the motor (40) to rotate the crucible (34) at a rotational speed which monotonically increases and decreases. A method for pulling a semiconductor crystal (58) is also disclosed which includes the steps of performing a Fourier analysis on a periodic signal for variably rotating a crucible (34); generating a sine wave which corresponds to a fundamental Fourier frequency of the periodic signal; and energizing the crucible motor (40) to rotate the crucible (34) at a rotational speed which increases and decreases as a function of the generated sine wave. Other apparatus and method for pulling crystals with the CZ method to achieve a desired oxygen concentration and gradient are also disclosed.