High Cx/Co 13nm-capacitive-gap transduced disk resonator

Electrode-to-resonator gaps as small as 13.2nm achieved on a 59.5-MHz capacitive-gap transduced disk resonator have now enabled a measured electromechanical coupling strength (C_x/C_o) greater than 1.62% at a bias voltage of only 5.5V while retaining an unloaded Q of 29,640, for a k_t²Q product of 480 that sets the record at VHF. Several key discoveries contribute to this successful demonstration, including a modified polysilicon etch recipe that enables considerably smoother etch sidewalls than previously achievable, allowing more uniform sidewall sacrificial layer deposition and preventing structure pull-in by removing asperities and their associated strong electric fields. This combination of high (G_x/C_o) and Q stands to reduce power consumption in low-noise oscillators, improve sensitivity for zero-quiescent all-mechanical receivers, and expand the range of filters accessible to capacitive-gap transduced resonators to more mainstream wireless communication applications with much improved insertion loss performance.