Optical effects of multilayer thin-film structures during zone-melting recrystallization with an infrared heat source

Abstract

Processing multilayer thin-film structures, such as silicon-on-insulator (SOI) wafers, with a radiant line heat source has been used extensively to recrystallize and improve the quality of specific films in the structure. The radiation heat transfer has been found to have the greatest impact on the success of the process. The amount of reflection and absorption of radiation emitted by the infrared heat source is influenced by the layering scheme and thicknesses of the films when these thicknesses are on the same order of magnitude as the wavelengths of the radiation. A two-dimensional numerical heat transfer model has been developed to account for the optical nature of the multilayer films during infrared processing. A numerical parametric study was conducted to evaluate the significance of varying the thickness of different layers of SOI wafers during zone-melting-recrystallization processing with a graphite strip heater emitting in the infrared spectrum. Results indicate that varying either the capping or insulating silicon oxide film causes significant fluctuations in the reflectivity and temperature profiles of the film. Increasing the thickness of the Si film results in small fluctuations of the reflectivity. A linear increase of the maximum temperature attained and the melt zone width was calculated for increasing thickness of the Si film. Sensitive layering schemes, where small variations in thickness may result in significant changes in reflectivity, were identified. The optical effects on the width and structure of the melt zone were investigated.