Total Ionizing Dose Effects in Piezoelectric MEMS Relays

This paper investigates total ionizing dose (TID) effects on the piezoelectric properties of lead zirconate titanate (PZT). The capacitance and contact voltage of thin-film, PZT-based relays were measured following incremental ⁶⁰Co TID irradiations. The devices were held in several different bias conditions, during exposure. The direction of the biasing electric field during exposure, along with the polarization prior to exposure, has a measurable impact on post-irradiation operating voltage of the relay. In all cases, the switching voltage, as obtained via the peak values in a capacitance versus voltage sweep, shifted in a direction that would minimize the switching electric field in the direction of pre-exposure polarization. These effects were observed to be both significantly greater than the shifts experienced by a set of control samples, as well as reversible via aging at room temperature. The devices display remarkable robustness, operating during active TID exposure [dose rate = 855.6 rad(Si)/s], failing at a TID greater than 15 Mrad(Si).