Crystal puller and method for growing monocrystalline silicon ingots

A method of growing a monocrystalline silicon ingot in a crystal puller of the type used for growing monocrystalline silicon ingots according to the Czochralski method, the crystal puller having a housing, a crucible in the housing for containing molten silicon and a pulling mechanism for pulling an ingot upward from the molten silicon within the housing, the method comprising the steps of:

• powering a first electrical resistance heater disposed in the housing generally above the crucible to radiate heat toward the ingot as the ingot is pulled upward within the housing;
• powering a second electrical resistance heater disposed in the housing in generally spaced relationship above the first electrical resistance heater to radiate heat toward the ingot as the ingot is pulled upward within the housing, the second electrical resistance heater having a heating power output substantially less than the heating power output of the first electrical resistance heater;
• the heating power output of the first and second heaters being sufficient to maintain the ingot above a predetermined temperature for promoting diffusion of intrinsic point defects;
• separating the ingot from the molten silicon once the ingot has been grown to approximately a predetermined length;
• and
• reducing the heating power output of the first and second electrical resistance heaters after separating the ingot from the molten silicon to substantially increase the cooling rate at which the ingot is cooled.