Abstract: Radiation heating of a semiconductor wafer employs first and second pluralities of spaced and skewed lamps. Lamps in each plurality are grouped beginning with the innermost lamps and extending to the outermost lamps. Each group of lamps in one plurality of lamps are interconnected with a group of lamps in the other plurality of lamps whereby the interconnected groups of lamps are simultaneously and equally energized. Lamp voltage is modulated in accordance with a preestablished table for each size of wafer and temperature cycle. Alternatively, temperature sensors can be employed to provide feedback to a computer controlled modulator. The lamps in the different groups can be selected to have different steady state power intensities for a given voltage to thereby establish a desired temperature gradient.