A system and method for etching workpieces in a uniform manner are disclosed. The system includes a semiconductor processing system that generates a ribbon ion beam, and a workpiece holder that scans the workpiece through the ribbon ion beam. The workpiece holder includes a plurality of independently controlled thermal zones so that the temperature of different regions of the workpiece may be separately controlled. In certain embodiments, etch rate uniformity may be a function of distance from the center of the workpiece, also referred to as radial non-uniformity. Further, when the workpiece is scanned, there may also be etch rate uniformity issues in the translated direction, referred to as linear non-uniformity. The present workpiece holder comprises a plurality of independently controlled thermal zones to compensate for both radial and linear etch rate non-uniformity.