A system for processing a workpiece includes a base having a bowl or recess for holding a processing fluid. A sonic energy source, such as a megasonic transducer, provides sonic energy into a processing fluid in the bowl. A process head holds a workpiece. A process head lifter lowers the head holding the workpiece into the processing fluid in the bowl. Sonic energy is provided to the workpiece through the processing fluid, optionally while the processing head spins the workpiece. The processing fluid may include de-ionized water and an etchant.