High-Q mechanical tuning of MEMS resonators using a metal deposition -annealing technique

A method for coarse and fine mechanical frequency tuning of MEMS resonators is presented in this paper. Controlled material deposition onto microresonator top surfaces enables resonance frequency shifts toward higher or lower frequency, depending on the resonator structural materials. An analytical derivation is presented and experimental testing on single-crystal silicon resonator beams coated with gold demonstrates the viability of the method. Resonance frequency shifts over 11% with a tuning resolution of 90 Hz/nm of deposited metal are recorded. The performances of the tuned resonators are investigated and modeled. Metal deposition on SCS resonators revealed large Q-decreases, from 25,000 to 5,000. A post-tuning annealing step, at temperature <300°C, is utilized to restore the initial high-Q of the resonators.