APPARATUS AND METHOD FOR ROTATING A CRUCIBLE OF A CRYSTAL PULLING MACHINE

摘要

APPARATUS AND METHODS FOR PULLING A SEMICONDUCTOR CYSTAL 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.