Measurements of wafer surface temperature during plasma etching, performed with a new optical contactless thermometer method, are presented. The respective effects of ion bombardment and chemical reaction on the increase in wafer temperature during plasma etching are evaluated separately. The time dependence of the silicon surface temperature is shown, as a function of the ion bombardment energy and flux on the surface, for both rf and dc applied biases on the wafer. Sample heating resulting from the exothermic chemical reaction of silicon etching by fluorine is demonstrated.