The present invention provides a temperature controlled energy transparent window or electrode used to advantage in a substrate processing system. The invention also provides methods associated with controlling lid temperature during processing and for controlling etching processes. In a preferred embodiment the invention provides a fluid supply system for the lid which allows the fluid to flow through a feedthrough and into and out of a channel formed in the window or electrode. The fluid supply system may also mount the window or electrode to a retaining ring which secures the window or electrode to the chamber. In another aspect the invention provides a bonded window or electrode having a first and second plate having a channel formed in the plates so that when the plates are bonded together they form a channel therein through which a temperature controlling fluid can be flowed. An external control system preferably regulates the temperature of the fluid.