Patent ID: 8334194

Claim:
A method for fabricating a semiconductor wafer, said method comprising: applying a layer of semiconductor material across a portion of a setter material; introducing the setter material and the semiconductor material to a predetermined thermal gradient region to form a melt, the predetermined thermal gradient region including a predetermined nucleation and growth region; and inducing crystallization by positioning the melt adjacent a heat extractor in the nucleation and growth region, the heat extractor comprising a surface bearing a pattern wherein at least a first portion of the surface is closer to the melt than a second portion of the surface so that the heat extractor cools a first portion of the melt that is adjacent the first portion of the surface faster than a second portion of the melt that is adjacent the second portion of the surface so as to form at least one local cold spot in the layer of semiconductor material in which crystal nucleation commences before crystal nucleation commences in another location in the layer of semiconductor material.