Thermal radiation modeling in multilayer thin film structures

Abstract

A general technique is developed to account for the microscale heat transfer effects involved with the interaction of thermal radiation and multilayer thin films. In particular, the microscale radiation effects involved with both the emission from the multilayer structure and the reflection of incident radiation are described in detail. Considerable optical interference within the structure occurs when the film thicknesses are on the same order of magnitude as the wavelengths of the incident or emitted radiation; therefore, the net surface reflectivity and emission from the film structure are altered by slight changes in film thickness. Consequently, during high temperature thermal processing of micron thickness films, the resultant temperature profiles and the quality of the processed structure will be affected. The reflectivities and emissivities are calculated numerically using the matrix method for several different layering structures subject to thermal radiation. For the special case of equal optical film thicknesses, cross-correlation peaks are identified; these layering schemes are very sensitive to small film thickness changes. Maximum temperatures attained during thermal processing are calculated for several specific film structures to illustrate the significance of these effects.