Capacitive sensing electrodes with reduced squeeze-film damping

This paper reports on a new design of closing-gap capacitive electrodes with reduced squeeze-film damping. In contrast to state of the art electrodes our electrode design incorporates small venting slits and therefore allows to significantly reduce the damping contribution of sense electrodes in MEMS inertial sensors with only minor reduction of electrical sensitivity. Our approach is realized by means of an advanced surface micromachining process featuring an additional polysilicon layer and suitable for mass production. We present a comprehensive proof of concept by means of CFD and electric field simulations as well as SEM images and measurement data obtained from fabricated test devices.