A centrifugal workpiece processor for processing semiconductor wafers and similar workpieces includes a head which holds and spins the workpiece. The head includes a rotor having a gas system. Gas is sprayed or jetted from inlets in the rotor to create a rotational gas flow. The rotational gas flow causes pressure conditions which hold the edges of a first side of the workpiece against contact pins on the rotor. The rotor and the workpiece rotate together. Guide pins adjacent to a perimeter may help to align the workpiece with the rotor. An angled surface helps to deflect spent process liquid away from the workpiece. The head is moveable into multiple different engagement positions with a bowl. Spray nozzles in the bowl spray a process liquid onto the second side of the workpiece, as the workpiece is spinning, to process the workpiece. A moving end point detector may be used to detect an end point of processing.