Patent ID: 6726764
Filing Date: 2004-04-27
Classification: C30B,Y10T

Abstract:
A control method for use with a crystal puller for growing a monocrystalline semiconductor crystal according to the Czochralski process, said crystal puller having a heated crucible containing a semiconductor melt from which the crystal is grown at a growth rate Vg, said melt having a surface forming a meniscus adjacent the crystal, said crystal puller further having a heater supplied by a power supply for heating the crucible, said crystal being grown on a seed crystal pulled from the melt at a pull rate Vp, said method comprising the steps of:defining an interval of time for observing growth of the crystal being pulled from the melt; determining variations in crystal diameter occurring during the observation interval; estimating a current value of the growth rate Vgf as a function of the determined variations in crystal diameter; estimating a current steady-state value of the growth rate Vgs as a function of the estimated growth rate Vgf at the end of the observation interval; determining a pull rate parameter as a function of the estimated steady-state growth rate Vgs and independent of a temperature condition sensed during pulling, said pull rate parameter being representative of an incremental change in the pull rate Vp to effect a desired change in the diameter of the crystal toward a target diameter; determining a heater power parameter as a function of the estimated steady-state growth rate Vgs and independent of a temperature condition sensed during pulling, said heater power parameter being representative of an incremental change in the power supplied to the healer to effect a desired change in the growth rate of the crystal toward a target growth rate; and adjusting the pull rate Vp according to the pull rate parameter and adjusting the power supplied to the heater by the power supply according to the heater power parameter thereby minimizing variations in both crystal diameter and growth rate during subsequent growth of the crystal following the observation interval.