A substrate heater comprising a ceramic substrate support having a substantially flat upper surface for supporting a substrate during substrate processing; a resistive heater embedded within the substrate support; a heater shaft coupled to a back surface of the substrate support, the heater having an interior cavity that extends along its longitudinal axis and ends at a bottom central surface of the substrate support; and a supplemental heater, separate from the ceramic substrate support, positioned within the interior cavity of the heater shaft in thermal contact with a portion of the bottom central surface of the substrate support such that the supplemental heater can alter the temperature of a central area of the upper surface of the substrate support.
