Structure and Stress Evolution in Polycrystalline Thin Films

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9710139 Thompson This is an experimental and theoretical research effort on the evolution of structure and the mechanical state of polycrystalline films during thin metal film deposition and during subsequent thermal processing. The goal of the research is to develop models and simulations which can be used to predict the course of grain size, grain orientation and stress evolution as a function of substrate, film and capping layer material properties, while also considering the deposition conditions and subsequent thermal history. The stresses in films deposited on substrates are monitored using wafer curvature measurements made while heating at controlled and variable rates and while annealing at different temperatures for different times. Film material, capping layers, film thickness, and film deposition temperature are among the varied parameters in these experiments. In situ TEM observations explore grain structure evolution in heated films on thin substrates which impose a strain in the films due to differential thermal expansion. Texture of the films is monitored by X-ray analyses. %%% As modeling and simulation capabilities evolve through comparison with experiments, new quantitative capabilities are developed for predicting grain structure, grain orientation, and stress evolution. This provides techniques for processing of films with properties that are optimized for specific engineering applications. Polycrystalline films are used in electronic, micromechanical, and magnetic devices. In these applications, the performance and reliability of polycrystalline films are strongly affected by their structure, specifically the distribution of grain sizes and crystallographic orientations. ***