Micromechanical "hollow-disk" ring resonators

Abstract

A vibrating polysilicon micromechanical "hollow-disk" ring resonator obtained by removing quadrants of material from a solid disk resonator, but purposely leaving intact beams of material to non-intrusively support the structure, has been demonstrated in several vibration modes spanning frequencies from HF (24.4 MHz), to VHF (72.1MHz), to UHF (1.169 GHz), with Q's as high as 67,519, 48,048, and 5,846, respectively. Furthermore, the use of notched support attachments closer to actual extensional ring nodal points raises the Q to 14,603 at 1.2 GHz, which is the highest yet achieved past 1 GHz, and which clearly illustrates the utility of notching for substantially higher Q. At 1.2 GHz, a combination of high Q and larger capacitive transducers allows the notched version to achieve an R/sub x/ of only 282 k/spl Omega/, which is 12X smaller than achieved by previous pure polysilicon surface-micromachined solid disk resonators in the GHz range.