Patent ID: 7611580

Claim:
A system for controlling crystal growth in a crystal growing apparatus, said crystal growing apparatus having a heated crucible including a semiconductor melt from which a monocrystalline ingot is grown according to a Czochralski process, said ingot being grown on a seed crystal pulled from the melt, said melt and said ingot forming a melt-solid interface therebetween, said system comprising: first and second coils positioned near the crucible for applying a cusped magnetic field to the melt; a variable power supply for energizing the coils to produce the magnetic field applied to the melt; and a controller for varying the power supply while the ingot is being pulled from the melt, said variable power supply being responsive to the controller for varying the magnetic field to control cusp position of the magnetic field relative to the melt-solid interface between the melt and the ingot to control a shape of the melt-solid interface, said controlled shape of the melt-solid interface being a function of length of the ingot.