Capacitive transducer strengthening via ald-enabled partial-gap filling

Abstract

The electromechanical coupling factors (ηe’s) of capacitively-transduced micromechanical resonators have been increased by a factor of 8.1× via a process technology that utilizes atomic layer deposition (ALD) to partially fill the electrode-to-resonator gaps of released resonators with high-k dielectric material and thereby achieve effective electrode-to-resonator gap spacings as small as 32 nm. The electromechanical coupling increase afforded by gaps this small not only lowers termination impedances for capacitively-transduced micromechanical filters from the kΩ range to the sub-100Ω range, thereby making them compatible with board-level RF circuits; but does so in a way that reduces micromechanical filter termination resistance RQ much faster than the electrode-to-resonator overlap capacitance Co, thereby also substantially increasing the 1/(RQCo) figure of merit (FOM).