Complete Modeling of a Light-Pipe Radiation Thermometer in a Rapid Thermal Processing System

Light-pipe radiation thermometers are predominantly used to monitor wafer temperature during rapid thermal processing (RTP) of semiconductors. The processes used in fabrication of semiconductor devices during rapid thermal processing are extremely temperature sensitive and the errors associated with light-pipe measurements are great concerns across the industry. Modeling of the light-pipes has helped in understanding 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 has not been possible due to the computational demand. In this paper, the reverse Monte Carlo method is used to model the signal transport through a light-pipe thermometer used in a RTP system. The Monte Carlo model considers the spectral and angular dependent optical properties of the chamber and quartz materials. The reverse Monte Carlo model is applied to the full scale instrumented system with characteristics of a RTP system with a quartz light pipe probe and the results are compared against previously published measurements from the same system.