A digital holographic microscope for complete characterization of microelectromechanical systems

Digital holographic microscopy (DHM) can be described as a non-invasive metrological tool for inspection and characterization of microelectromechanical structures (MEMS). DHM is a quick, non-contact and non-invasive technique that can offer a high resolution in both lateral and vertical directions. It has been employed for the characterization of the undesired out-of-plane deformations due to the residual stresses introduced by technological processes. The characterization of these deformations is helpful in studying and understanding the effect of residual stress on the deformation of a single microstructure. To that end, MEMS with different geometries and shapes, such as cantilever beams, bridges and membranes, have been characterized. Moreover, DHM has been applied efficiently to evaluate variations of the structure profile due to some external effects. As an example, the characterization of a cantilever subjected to a thermal process has been described. The results reported show that DHM is a useful non-invasive method for characterizing and developing reliable MEMS.