Noncontact quantitative spatial mapping of stress and flexural rigidity in thin membranes using a picosecond transient grating photoacoustic technique

This paper describes a purely optical technique for measuring and spatially mapping out stress and rigidity in thin membranes. Its application to a membrane of aluminum nitride that has significant spatial nonuniformities in its elastic properties demonstrates the method. The attractive features of this technique - fast, noncontacting measurement, good spatial resolution, ability to quantify in-plane anisotropy - make it potentially useful for characterizing elements of microelectromechanical structures, masks for advanced lithography systems, acoustic filters, and other devices in which the mechanical properties of membranes are important.