Parameter extraction from simple electrical measurements on surface micromachined cantilevers

In surface micromachined structures, many parameters like geometry and Young's modulus depend on the process steps and need to be measured for accurate prediction of their functionality. This work discusses simple electrical measurement techniques on surface micromachined cantilever beams to determine Young's modulus, the gap between the beam and the substrate, and the thickness of a deposited aluminum layer on the beam. Cantilevers are ubiquitous in most microelectromechanical system (MEMS) sensors and actuators, and hence are ideal test structures. Pull-in, and a novel resonance frequency measurement based on the pull-in technique, are done on oxide anchored doped polysilicon beams at the wafer level, and some of the device and material properties are extracted from these measurements. The extracted values are compared with those determined from established methods like vibrometry and surface profiler measurements, and show good agreement. Since the measurements are all electrical, they can be part of standardized testing and are also suitable for packaged devices.