Effect of surface roughness on the temperature of a silicon wafer heated by incoherent radiation

The effect of surface roughness of a silicon wafer on its temperature on heating by incoherent radiation is studied. The temperature-time diagrams of heating and cooling are obtained experimentally for double-side- and single-side-polished wafers at different arrangements of the rough surface with respect to the radiation source. The steady-state temperatures of such wafers under identical conditions of heating from 100 to 250°C are compared. It is established that the highest steady-state temperatures are common to the wafers presenting their rough side to the radiation source, the lowest steady-state temperatures to the double-side- polished wafers, and the intermediate temperatures to the wafers presenting their polished side to the radiation source. An optical model of the rough surface is suggested. In this model, the rough surface is represented by a negligibly thin damaged layer characterized by its own optical parameters. In the model, an optical parameter is introduced to characterize the degree of roughness of the illuminated surface. The dependence of the absorptivity of the wafer on this parameter and on the arrangement of the rough surface with respect to the radiation source is treated theoretically. The model provides a qualitative interpretation of the experimental data.