Photothermoelastic evaluation for small mechanical structures

We describe a photothermal technique for testing the mechanical properties of small mechanical structures. Irradiation with chopped laser light on platelike or beamlike structures produces flexural vibration caused by thermoelastic bending. By monitoring the vibration, we can develop useful techniques for evaluating thickness, size attachment, tension, and adhesion of small mechanical structures. The technique will he useful for inspecting small mechanical structures that are fabricated with lithographic processes for various high technology applications.