Reliability of etching angle estimation of MEMS resonators from electrical measurements

This paper focuses on the determination of etching imperfections based on electrical measurements in electrostatic MEMS. It aims at providing results and methodology to experimenters to help them determine under which conditions they should operate a MEMS electrostatic resonator to estimate etching defects such as the mean etching angle. We analyze the parameters of interest for such a study and show how to evaluate the driving level required for a reasonable estimation. The method is based on an analytical expression of the electrostatic force and squeeze-film damping taking into account the non-ideal verticality of the electrodes due to the etching process. We prove that the aspect ratio of the resonator is a critical parameter that strongly impacts the precision of the estimation.