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Side-Supported Radial-Mode Thin-Film Piezoelectric-on-Silicon Disc Resonators
摘要： In this paper, anisotropy of single crystalline silicon (SCS) is exploited to enable side-supported radial-mode thin-film piezoelectric-on-substrate (TPoS) disc resonators. In contrast to the case for isotropic material, it is demonstrated that the displacement of the disc periphery is not uniform for the radial-mode resonance in SCS discs. Specifically, for high order harmonics, nodal points are formed on the edges, creating an opportunity for placing suspension tethers and enabling side-supported silicon disc resonators at very-high-frequency (VHF) band with negligible anchor loss. In order to thoroughly study the effect of material properties and the tether location, anchor loss is simulated using a 3D perfectly-matched-layer (PML) in COMSOL. Through modeling, it is shown that 8th harmonic side-supported SCS disc resonators could potentially have orders of magnitude lower anchor loss in comparison to their nano-crystalline diamond (NCD) disc resonator counterparts given the tethers are aligned to the [100] crystalline plane of silicon. It is then experimentally demonstrated that in thin-film piezoelectric-on-silicon disc resonators fabricated on an 8μm silicon-on-insulator (SOI) wafer, unloaded quality factor improves from ~450 for the second harmonic mode at 43 MHz to ~11,500 for the eighth harmonic mode at 196 MHz if tethers are aligned to [100] plane. The same trend is not observed for NCD disc resonators and SCS disc resonators with tethers aligned to [110] plane. Finally, temperature coefficient of frequency (TCF) is simulated and measured for the radial-mode disc resonators fabricated on the 8μm thick degenerately n-type doped SCS and the TFC data is utilized to guarantee proper identification of the harmonic radial-mode resonance peaks amongst others.
关键词： perfectly matched layer,silicon disc resonator,radial mode,quality factor,anchor loss
更新于2025-09-19 17:15:36
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Influences of relative humidity on the quality factors of MEMS cantilever resonators in gas rarefaction
摘要： In this paper, the effect of relative humidity of moist air is discussed on the quality factor (Q factor) of micro-electro-mechanical systems (MEMS) cantilever resonators in wide range of gas rarefaction (ambient pressure and accommodation coefficients, ACs). The modified molecular gas lubrication (MMGL) equation is used to model the squeeze film damping problem of MEMS cantilever resonators. Dynamic viscosity and Poiseuille flow rate are used to modify the MMGL equation to consider the coupled effects of relative humidity and gas rarefaction. Thermoelastic damping and anchor loss, which are dominant damping mechanisms of MEMS cantilever resonators, are also included to calculate total Q factor. Thus, the influences of relative humidity are discussed on the Q factors of MEMS cantilever resonators in wide range of gas rarefaction and dimension of cantilever. The results showed that the Q factor decreases as relative humidity increases in wide range of gas rarefaction (pressure, and ACs) and dimension of cantilever (length, width, and thickness). The influences of relative humidity on the Q factor become more significantly in larger length, larger width, smaller thickness of cantilever, and higher gas rarefaction (lower pressure and ACs). Whereas, the influences of relative humidity on the Q factor reduce or are neglected in smaller length, larger thickness of cantilever and lower gas rarefaction (higher pressure and ACs).
关键词： Anchor loss,Relative humidity,Quality factor,Gas rarefaction,Squeeze film damping,Thermoelastic damping,MEMS cantilever resonators
更新于2025-09-10 09:29:36