Effects of radiative properties of surfaces on radiometric temperature measurement

A Monte Carlo model has been developed to simulate the radiative process and to predict the effective emissivity for accurate radiometric temperature measurements in rapid thermal processing (RTP) furnaces. The effective emissivity used here takes into consideration the limited numerical aperture of the lightpipe. The bidirectional reflectance distribution function (BRDF) is applied to describe the angular distribution of the reflected energy. After comparing several BRDF models, we recommend two simple modified models for use in the Monte Carlo method. The comparison between the modeling results from the BRDF model and the specularity model validates the usage of the BRDF models and makes it attractive to obtain the BRDF through characterizing the surface roughness.