Patent ID: 8367983

Claim:
A system for processing a substrate, comprising: a heat source to provide radiation in a first range of wavelengths; a pyrometer to measure the temperature of the substrate when the substrate is disposed on a substrate holder within a process area of the chamber by detecting radiation in a second range of wavelengths within the first range of wavelengths; and a window between the heat source and the substrate holder, the window being made from a material which is transparent to radiation in the first range of wavelengths and having a first reflective coating and a second reflective coating on a surface between the heat source and the substrate holder, the reflective coatings being reflective to radiation in the second range of wavelengths, wherein the window is effective to prevent radiation within the second range of wavelengths from being transmitted to the pyrometer, wherein the window comprises a first window element having a first surface facing the heat source and a second surface facing the substrate holder and one of the first reflective coating and the second reflecting coating is on the first surface and the first reflective coating and the second reflective coating having a range of reflective wavelengths that overlap.