Asymmetrically Configured MEMS Spiral Resonator with Ultrathin Internal Electrostatic Transduction

This paper introduces an internal electrostatic transduced resonator with asymmetrical drive/sense configuration to achieve signal amplification with low $R_{m}$ at higher modes. The device operates as a resonant transformer that can be used to increase voltage levels or transform impedances. The structure comprises a metal-dielectric-metal spiral ring with a 12.7nm Al2O3 internal dielectric layer. Measured results show the device has mode frequency of 7.19 MHz and $R_{m}$ of $1.43 \mathrm{k} \Omega$ at a 3 V bias. The dynamic $C_{D}=24.87~{\mathrm {nF}}$ and ${\mathrm {C_{s}}}=70.54 \mathrm{nF}$, results in a nominal ${\mathrm {C_{D}}}: {\mathrm {C_{S}}}={\mathrm {1}}: {\mathrm {2.84}}$ ratio. The resonant frequency of the structure can be tuned by applying a common bias to sense and drive mode, while the capacitance ratio can be tuned by varying the differential bias between the drive and sense ports. Our measurements show that this ratio can be tuned from 1.86 at 1 V bias to 5.12 at 3 V bias at the sense port. This capacitance transformation holds promise for signal amplification, as well as for designing low-loss matching networks.