an apparatus for processing wafer - shaped articles comprises a rotary chuck adapted to hold a wafer shaped article of a predetermined diameter in a predetermined orientation . the chuck includes a heater comprising a plurality of gas nozzles directed toward a surface of a wafer shaped article when held by the chuck . the heater comprises a gas inlet and at least one heating element for heating gas to be discharged through the plurality of gas nozzles . the heater is configured to heat a wafer shaped article principally by convective heat transfer from heated gas discharged through the plurality of gas nozzles .