Semiconductor processing temperature control

A temperature control system having a re-circulation loop that uses valves to selectively circulate a temperature control fluid through a cooling system, through a heating system, or through a through passage so as to controlling the temperature of the temperature control fluid, which, in turn, controls the temperature of a target. A temperature sensor monitors the target's temperature. A controller controls valve operation in response to the temperature measured by the temperature sensor to obtain a predetermined target temperature. Beneficially, the controller controls the target's temperature according to a predetermined temperature profile. Continuous etching along a predetermined temperature profile is possible.