Nickel Vibrating Micromechanical Disk Resonator with Solid Dielectric Capacitive-Transducer Gap

A MEMS-based vibrating disk resonator fabricated in a low temperature nickel metal material and using a 30-nm nitride dielectric capacitive transducer has been demonstrated at frequencies approaching 60 MHz with Q's as high as 54,507, which is the highest to date for any micro-scale metal resonator in the VHF range. The frequency-Q product of 3.3times10
¹²
achieved by this device is three orders of magnitude higher than the 1.1times10
⁹
of previous nickel micromechanical resonators. The degree of isolation afforded by its supports strongly governs the achievable Q's of this device, which vary from 490 when a 2 mum-radius supporting stem is used, to 54,507 when no stem is used, clearly indicating an anchor dominated loss mechanism, but more importantly indicating that nickel's intrinsic material Q is quite high at VHF. Furthermore, because its highest process temperature is 380degC, and there are paths to an even lower temperature ceiling (e.g., 100degC), the fabrication process for nickel disks is amenable to post-processing over finished foundry CMOS wafers, even those using advanced low-k dielectrics around copper metallization. Nickel material thus presents an intriguing path towards a complete communication transceiver (including all high Q passives) on a chip