An Effective Emissivity Model for Rapid Thermal Processing Using the Net-Radiation Method

A reflective shield has been placed in the lower chamber of some rapid thermal processing (RTP) systems so that the temperature of the silicon wafer can be accurately measured in situ with light-pipe radiometers. Better knowledge of the effective emissivity of the wafer reduces the uncertainty in the temperature measurement. This paper describes an enclosure model based on the net-radiation method for predicting the effective emissivity of the wafer. The model treats the surfaces in the enclosure as diffuse emitters, with a reflectivity that may include a diffuse component and a specular component. Using this model, a parametric study is performed to investigate the influence of the geometric arrangement, surface temperature and properties, and wavelength on the effective emissivity. The algorithm developed in this work may serve as a tool to improve radiometric temperature measurement in RTP systems.