Low voltage — Enhanced actuation MEMS cantilevers using Al2O3-SiO2 electrets

This work introduces a new technique of producing electrets using Al₂O₃-SiO₂ bilayer dielectric stack deposited by atomic layer deposition (ALD) technique. The surface potential of the charged electret was -100V corresponding to a negative charge density of ~12pC/cm². Microcantilevers patterned on this layer responded to voltages as low as 1V_pp, indicating their potential use as high efficiency actuators. The electret retained its charge for as long as 5 weeks in 0.1 mTorr vacuum without any surface treatments. The plasma-assisted atomic layer deposited SiO₂ layer with its higher bandgap of 9 eV produces the charges that are trapped in the lower bandgap Al₂O₃ away from the surface. The superlattice produced by Al₂O₃/SiO₂ stack contains the charges and prevent discharge.