AlN micromechanical radial-contour disc resonator

Micromechanical resonators that have high performance and are small in size are competitive candidates for radio frequency (RF) device minimization, paving the way for high performance monolithic transceivers. A piezoelectric aluminium nitride radial-contour mode disc resonator with a CMOS-compatible fabrication process is presented. The piezoelectric properties of the resonator disc, concerning the driving voltage and resonance mode deformation, are analysed, revealing the advantages introduced when using a sputter deposited AlN thin film. The radial-contour resonance mode of the disc resonator was investigated by finite element method simulation and theoretical evaluation. The resonance frequency was found to be thickness-independent, which is beneficial for fabrication and integration. In view of CMOS compatibility, a fabrication process with a low thermal budget and a tungsten titanium sacrificial layer was designed; devices were fabricated on 4 inch silicon wafers. The RF performance of the resonators with a diameter of 150 μm was measured using a HP4395A network analyzer, yielding a resonant frequency of 14.11 MHz with a Q value of 3125 and a return loss of 31.46 dB. These results indicate that this device is attractive for use in RF frequency-selecting and generation devices in high performance wireless communication systems.