Design-dependent Q-factor spectroscopy: Impact of surface oxidation on dissipation in 2 micrometer thick MEMS resonators

Abstract

Several intrinsic and extrinsic contributing loss mechanisms make the estimation of the total Q-factor Q of MEMS resonators challenging, as it is influenced by many parameters. Experimentally, however, only the total Q-factor of a vibrational mode can be measured; so for the study of environmental conditions, pressure and temperature sweeps are typically performed to provide knowledge about fluidic and thermo-elastic dissipation. However, the contributing amounts of intrinsic damping mechanisms cannot be split into their individual components. In this study, we explore the dynamics of many non-slender MEMS resonators while varying the width. We call this technique design-dependent Q-factor spectroscopy (DDQS). The use of hundreds of devices with several out-of-plane resonance modes within DDQS allows the separation of the total Q-factor into the different dissipation mechanisms in thin films and MEMS resonators. Experimental results discussed alongside theoretical predictions indicate how the variation of a geometrical parameter of the resonator allows access to frequency regions with different dominant dissipation mechanisms. Furthermore, we evaluate the impact of surface-related losses and fluidic damping, showing a two-fold improvement in Q by removing the native grown silicon dioxide layer under high vacuum conditions. Our results highlight the advantages of optimizing the design of MEMS resonators within DDQS to understand the contributions to energy dissipation and lead to a new MEMS design approach.