High-Q UHF micromechanical radial-contour mode disk resonators

A micromechanical, laterally vibrating disk resonator, fabricated via a technology combining polysilicon surface-micromachining and metal electroplating to attain submicron lateral capacitive gaps, has been demonstrated at frequencies as high as 829 MHz and with Q´s as high as 23 000 at 193 MHz. Furthermore, the resonators have been demonstrated operating in the first three radial contour modes, allowing a significant frequency increase without scaling the device, and a 193 MHz resonator has been shown operating at atmospheric pressure with a Q of 8,880, evidence that vacuum packaging is not necessary for many applications. These results represent an important step toward reaching the frequencies required by the RF front-ends in wireless transceivers. The geometric dimensions necessary to reach a given frequency are larger for this contour-mode than for the flexural-modes used by previous resonators. This, coupled with its unprecedented Q value, makes this disk resonator a choice candidate for use in the IF and RF stages of future miniaturized transceivers. Finally, a number of measurement techniques are demonstrated, including two electromechanical mixing techniques, and evaluated for their ability to measure the performance of sub-optimal (e.g., insufficiently small capacitive gap, limited dc-bias), high-frequency, high-Q micromechanical resonators under conditions where parasitic effects could otherwise mask motional output currents. [1051].