| This dissertation presents simulation, fabrication and testing of micromachined acoustic resonators with high quality factor and their applications in radio-frequency and biomedical engineering fields.; One-dimensional Mason model is introduced and employed to simulate behaviors of FBARs composed of Al/ZnO/Al/SiN layers. The experimental results have a good match with the simulation results.; To minimize energy loss to the substrate and achieve high Q, an FBAR with a novel structure (Al/ZnO/Al active area is isolated from the substrate) is fabricated. The newly fabricated FBAR achieves a Q of about 1,300 and K t2 of 6.8%, four times and twice that of a conventional FBAR with no isolation, respectively.; High-tone bulk acoustic resonators (HBARs) have been fabricated on four types of substrates: c-axis sapphire, AT-cut crystal quartz, fused silica, and <100> single crystal silicon. Q of 51,000 for the HBAR on the sapphire substrate is obtained. Q's of the HBARs on the other substrates have also been reported. Temperature effect on the Q and resonant frequency of the four types of HBARs has been investigated.; Colpitts voltage controlled oscillator (VCO) at 1.1GHz is designed with an FBAR as the frequency control element. The oscillator achieves an extremely low phase noise of -115 dBc/Hz at 10kHz offset, which is 19dB better than that of an LC oscillator. Voltage control of the oscillation frequency is obtained by applying a DC voltage on the FBAR.; FBAR as a highly sensitive mass sensor that can operate in vapor and liquid is presented. Mass sensitivity and minimum detectable mass in both air and liquid environments are investigated.; FBAR with a thin Au film deposited on the surface for detecting Hg 2+ ion is described. The FBAR sensor detected as low as 10 -9 M Hg2+ (0.2 ppb Hg2+) in water. K+, Ca2+, Mg2+, Fe2+, Zn2+, Ni2+ had little or no effect on the resonant frequency of the FBAR.; FBAR with its Au-coated surface immobilized with thiol-modified biotin has been used to observe protein-ligand interactions. With the FBAR surface immobilized with a single-strand DNA, hybridization of DNA' can be detected by the FBAR. The FBARs have advantages such as micrometers sizes (need only tiny amount of sample), label-free and real-time analysis capability, and adaptability in array formats for simultaneous analysis of multiple targets. These advantages make FBAR an attractive candidate in DNA or protein chip technologies.; A micromachined SU-8 probe with an integrated FBAR mass sensor at its tip is fabricated. The probe can be conveniently inserted into biological and chemical environments to sense various chembio species, and has been shown to detect mercuric ions in water with outstanding selectivity and sensitivity. |
