High-Q bulk-mode SOI square resonators with straight-beam anchors

Abstract

In this paper, the performance of 6.35 MHz Lamé-mode square resonators with different dimensions of straight-beam anchor supports is presented, with quality factor values exceeding one million in ambient pressures as high as 150 Pa. A maximum Q value of 1.70 million was experimentally measured for some of the square resonators at a vacuum pressure of 36 νTorr. The Q values of square resonators were relatively independent of pressure at levels below 100 Pa, which suggests that Q is pressure limited due to air damping only when pressures become higher than 100 Pa. Dimensions of straight-beam anchors placed at the four corners of the square resonator lead to tradeoffs among achievable Q, power handling capabilities and motional resistance. Longer anchor beams generally provide good signal-to-noise performance of a square resonator at lower dc bias; however, the resonator goes into the nonlinear regime at lower ac-dc drive amplitudes, which means reduced power handling capability. The benefit of shorter anchors is that the resonator is able to operate in a linear mode under high drive conditions. Depending on the type of application, anchor dimensions can be chosen such that the resonator's performance is optimal in terms of a quality factor, motional resistance and power handling. The resonators were fabricated using the silicon-on-insulator multi-user MEMS process from MEMSCAP. © 2009 IOP Publishing Ltd.