Monte Carlo Modeling of a Light-Pipe Radiation Thermometer

Light-pipe radiation thermometers (LPRTs) are widely used to monitor temperature during thermal processing of materials, particularly semiconductor wafer rapid thermal processing. According to the International Technology Roadmap for Semiconductors 2004, temperatures for semiconductor wafer processing should be measurable to within an uncertainty of $\pm$ 1.5 $^{\circ}$C at 1000 $^{\circ}$C with temperature calibration traceable to International Temperature Standard-90. To achieve this accuracy level, the radiation signal transport process inside the light-pipe probe has to be fully understood. Few studies have been conducted to model the radiation transfer of LPRTs. In this paper, a Monte Carlo model has been created to simulate the signal transport from the measurement surface through the light-pipe probe. The model predicts the acceptance angle or aperture of the light-pipe. We also investigated the effect of nonspecular reflections caused by the sidewall surface roughness of the light-pipe probe using this model.