Reverse Monte Carlo Modeling of Signal Transport in Light-Pipe Radiation Thermometers

Rapid thermal processing (RTP) has been widely used by the semiconductor manufacturing industry. Light-pipe radiation thermometers are the predominant method to monitor the wafer temperature during rapid thermal processing. The errors associated with light-pipe measurements are great concerns across the industry due the extreme temperature sensitivity of the processes used to fabricate semiconductor devices during rapid thermal processing. Modeling of the light-pipes has helped understand the signal transport process and errors associated with the light pipe measurements. However, due to the smaller size of the light-pipe sensor area with respect to the total system area full scale modeling of such a system including the light pipe thermometer have not been possible due to the computational demand. In this paper, a reverse Monte Carlo method is developed to model the signal transport through a light-pipe thermometer used in a RTP system. The Monte Carlo model considers the spectral and angle dependent optical properties of the chamber and quartz materials. The reverse Monte Carlo model is applied to a simpler system with a quartz light pipe probe for verification against a model developed using a forward Monte Carlo method.