A multilayer structured thin film system, such as a biomedical thin film, MEMS (Micro Electric Mechanical System)/NEMS (Nano Electric Mechanical System) devices, and semiconductors, is widely used in various fields of industries. To non-destructively evaluate the multilayer structured thin film system, a mechanical scanning acoustic reflection microscope has been well recognized as a useful tool in recent years. Especially, the V(z) curve method with the scanning acoustic microscope is used to characterize the very small area of the system. In this study, V(z) curve simulation software for simulating transducer output when we transmit an ultrasound wave into the specimen has been developed. In the software, the Thompson-Haskell transfer matrix method is applied to solve for the reflectance function. All input and output interfaces incorporated in a GUI interface for users’ convenience. Surface acoustic wave velocities are calculated from the simulated V(z) curves. For the precise calculation advanced signal processing techniques are
utilized. The surface acoustic wave velocity is compared to that from an experiment with a bulk solid. We also tested the simulation’s thickness sensitivity by simulating models with different thickness in nanoscale. A series of experiments with multilayered solids are carried out and the results are compared with the simulation results. It was the first time a comparison of analytical versus experimental for V(z) curves for multilayered system were performed. For the multilayered specimen, silicon (100) is used as a substrate. Titanium (thickness: 10 nanometer) and platinum (thickness: 100 nanometer) are deposited respectively.
Ultrasonic-Atomic Force Microscopy (U-AFM) was applied to determine the feasibility of visualizing interior features in an ultra-thin film system. As the amplitude and phase of the cantilever resonance frequency changes with local contact stiffness, U-AFM can obtain both surface and subsurface topographic and elastic images. Specimens with nanostructured silicon dioxide (SiO2) patterns deposited on silicon (111) surfaces were fabricated and covered with polymethyl methacrylate (PMMA) films with thicknesses of 800 nm and 1400 nm, respectively. While subsurface features were barely distinguishable beneath the 1400 nm film, 100 nm SiO2 features were clearly visualized for PMMA film thicknesses below and up to 800 nm. This research demonstrates the potential of U-AFM as a powerful technique for visualizing nanoscale subsurface features in microelectronic devices.