Electrical heater for crystal growth apparatus with upper sections

Abstract

An electrical resistance heater for use in a crystal puller used for growing monocrystalline silicon ingots according to the Czochralski method comprises a heating element sized and shaped for disposition in the housing of the crystal puller around the crucible for applying heat to the crucible and silicon therein. The heating element includes heating segments connected together in an electric circuit. The segments have upper and lower sections and are arranged relative to each other so that when disposed around the crucible containing molten silicon the upper sections are disposed generally above a horizontal plane including the surface of the molten silicon and the lower sections are disposed generally below the horizontal plane. The upper sections are constructed to generate more heating power than the lower sections thereby to reduce a temperature gradient between the molten silicon at its surface and the ingot just above the surface of the molten silicon. The upper sections have a thickness substantially equal to the thickness of the lower sections and have a width substantially less than the width of the lower sections. The cross-sectional area of the upper sections is everywhere less than the cross-sectional area of the lower sections.