The present disclosure suggests apparatus and methods that can be used to chemically process microfeature workpieces, e.g., semiconductor wafers. One implementation of the invention provides a method in which a surface of a microfeature workpiece is contacted with an etchant liquid. The wall of the processing chamber may be highly transmissive of an operative wavelength range of radiation, but the etchant liquid is absorptive of the operative wavelength range. The etchant liquid is heated by delivering radiation through the wall of a processing chamber. This permits processing chambers to be formed of materials (e.g., fluoropolymers) that cannot be used in conventional systems that must conduct heat through the wall of the processing chamber.