The emissivity of silicon wafers determine the temperature control in closed loop rapid thermal processing (RTP) systems. Silicon surface roughness, doping, and layers affect the intrinsic wafer emissivity, while RTP chamber walls reflectance reduces the amplitude of these effects. For temperatures below 600V, device side topography and layers also affect the emissivity of the wafer. Narrow band and wide band pyrometers show similar behavior with respect to layers on the wafer, as indicated by experimental and modeling techniques.