Influence of the window thermal diffusivity on the silicon wafer temperature in a rapid thermal system

Abstract

The heating of a silicon wafer in a rapid thermal process is studied by numerical simulation. In the model, the equations of conservation of mass and energy are solved with the finite volume method and the determination of the solutions of the radiative transfer equation is based on the Monte-Carlo method. The results of numerical simulations, without optimization and in steady-state, show a close relationship between the thermal profiles of the silicon wafer and the ones of the quartz window. By introducing a high thermal diffusivity value for the window, the homogeneity of the wafer temperature is improved by 54%. The effect of heat storage by the quartz window on the temperature profile of the silicon substrate is hence well appreciated. Finally, a selection of materials is proposed for the implementation of the high diffusivity infrared window.