Characterizing optically packaged MEMS & MOEMS devices using optical profiling techniques

Optical profiling (white light interferometry) has proven successful for measuring surface features of unpackaged MEMS devices. Most devices, however, perform differently once encased in their final packaging, which may include vacuum, elevated temperature or other special environments. This paper describes a novel interferometric surface profiling technique for high magnification measurement of devices through transparent packaging or environmental chambers. Three techniques are introduced into a long working distance interferometric objective: aberration correction, shaped illumination, and dispersive compensation. Data demonstrates that measurement results through the protective media are comparable to those of a standard objective measuring an unpackaged device.