High-Q Low-Impedance MEMS Resonators

摘要: Author(s): Hung, Li-Wen | Advisor(s): Nguyen, Clark T.-C. Abstract: The ever increasing need for regional and global roaming together with continuous advances in wireless communication standards continue to push future transceivers towards an ability support multi-mode operation minimal increases cost, hardware complexity, power consumption. RF channel-select filter banks pose a particularly attractive method achieving multiband reconfigurability, since they not only provide the needed front-end but also allow efficient versatile transceiver designs, e.g., software-defined radio. Such filters, however, impose requirements on their constituent resonators that are yet achievable micro-scale. Specifically, capacitively-transduced micromechanical achieve high Q, suffer from impedance; while piezoelectric offer low impedance, insufficient Q. This dissertation demonstrates four new techniques address issues both technologies.Two of methods recognize sub-30 nm gap spacing enables electrostatic acceptably impedance. Unfortunately, such small gaps aspect ratios difficult via wafer-level batch processing. Two proposed experimentally verified forming gaps: 1) partial-filling electrode-to-resonator atomic layer deposition (ALD) high-k dielectric; 2) generating volume reduction associated silicidation reaction. Among many benefits provided by silicide-based approach formation is speed release, where can be formed high-aspect-ratio microstructures released anneals lasting seconds few minutes, regardless lateral dimensions devices. Silicide-induced further does require any etching applicable wide range applications, electronics vacuum packaging.The next two seek circumvent fact AlN thin-film have historically been measured much lower Q than capacitive ones at similar frequencies. As result, it was commonly accepted thin films sputtered temperatures blame provides experimental evidence material loss restricts conventional resonators, rather losses contacting electrodes. transducer dubbed "capacitive-piezoelectric" introduced lifts electrodes away resonator tiny nanometer scale retain strong electric fields good electromechanical coupling, eliminating electrode-derived losses. After removing electrode losses, rise up 9 times. A surface-micromachining fabrication process has developed capacitive-piezoelectric metal separated air (or vacuum) gaps. second tapping uses Q-boosting mechanical circuits, electrode-equipped mechanically coupled electrode-less form composite-array. In this structure, energy shared among all composite-array effectively boost resonators. extrapolated measurement data 14,040 15,795. Both exceeding 10,000, posting highest reported constructed confirming indeed high-Q material.