Thin-film characterization and flaw detection. Final report, February 1, 1993--November 31, 1997

The objectives were to determine the elastic constants of thin films deposited on substrates, to measure residual stress and to detect and characterize defects in thin film substrate configurations. There are many present and potential applications of configurations consisting of a thin film deposited on a substrate. Thin films that are deposited to improve the hardness and/or the thermal properties of surfaces were of principal interest in this work. Thin film technology does, however, also include high {Tc} superconductor films, films for magnetic recording, superlattices and films for band-gap engineering and quantum devices. The studies that were carried out on this project also have relevance to these applications. Both the film and the substrate are generally anisotropic. A line-focus acoustic microscope has been used to measure the speed of surface acoustic waves (SAW) in the thin film/substrate system. This microscope has unique advantages for measurements in anisotropic media. Analytical and numerical techniques have been employed to extract the desired information on the thin film from the measured SAW data. Results include: (1) analytical and numerical techniques for the direct problem and for inverse methods; (2) measurements of homogeneous and superlattice film constants; (3) investigation of the effect of surface roughness and (4) measurements of residual stresses