199-MHz Polysilicon Micromechanical Disk Array-Composite Oscillator

The use of a stress-buffered array-composite of six 13.4-μm radius capacitive-gap transduced radial-contour mode polysilicon micromechanical disk resonators with 36.1-nm electrode-to-resonator gaps has enabled a Pierce oscillator centered at 199.2 MHz with phase noise marks of -104.7dBc/Hz at 1-kHz offset and -149.6dBc/Hz far from the carrier, sufficient for smartphones. The 12-kHz to 20-MHz integrated jitter is 163.3fs, which yields an excellent jitter FoM of -251dB. The key to this demonstration is the use of λ couplers to affect a 0° phase shift across the array terminals; and electrodeless resonators to buffer the effect of post-fabrication stress that otherwise might short disks to their electrodes when gaps are very small.