An apparatus for improving the temperature uniformity of a workpiece during processing is disclosed. The apparatus includes a platen having a separately controlled edge heater capable to independently heating the outer edge of the platen. In this way, additional heat may be supplied near the outer edge of the platen, helping to maintain a constant temperature across the entirety of the platen. This edge heater may be disposed on an outer surface of the platen, or may, in certain embodiments, be embedded in the platen. In certain embodiments, the edge heater and the primary heating element are disposed in two different planes, where the edge heater is disposed closer to the top surface of the platen than the primary heating element.