On the Air Damping of Micro-Resonators in the Free-Molecular Region

Predicting air damping on micromachined mechani-cal resonators is crucial in the design of high-performance filters used in wireless communication systems. In the past, most of the work focuses on devices in which con-tinuum theory can still be applied. In this work, we in-vestigate damping on oscillating structures caused by air in the free-molecular region in which continuum theory is no longer valid. Such a study is important for devices operated at a very low pressure or for those whose char-acteristic length is on the order of nanometers. A careful examination of the previous work has been conducted. Mistakes and limitations have been found and reported in this paper. A molecular dynamics simulation has been developed and used in predicting quality factors of an oscillating micro beam operated at low pressures. Simulation results have shown an excellent agreement with experimental data