Piezoelectric aluminum nitride vibrating RF MEMS for radio front-end technology

The demand of consumer electronics for RF filters and frequency reference elements has focused attention on the reduction of size, power consumption and price and pushed current research interests towards the manufacturing of a single-chip, integrated RF solution. Vibrating contour-mode MEMS resonators constitute the most promising technology for ultimately realizing this vision.; This dissertation presents analytical and experimental results on a new class of contour-mode aluminum nitride piezoelectric resonators. The realization of contour mode shapes in piezoelectric resonators, different from commercially available FBAR resonators for which the thickness sets the resonant frequency, permits the definition of multiple frequencies on the same silicon substrate in a very economical manner by using one sole lithographic step. Multi-frequency and multi-band single-chip resonant platforms can be fabricated using this new class of resonators. The use of piezoelectric transduction also has a definitive advantage over electrostatically-driven contour-mode resonators by solving the problem of large motional resistance. Piezoelectric body forces intrinsically offer higher electromechanical coupling coefficients than corresponding surface-based electrostatic forces, making possible low values of motional resistance and the direct interface of these devices with 50 O systems. Experimental results from different contour-mode structures have demonstrated that rectangular plates and circular rings constitute the most promising topologies for the realization of next-generation multi-frequency resonant platforms. Rectangular plate resonators have shown, for example, quality factor, Q, of 2,100 in air and motional resistance of 125 O at a frequency of 85 MHz. At the same time circular ring resonators were fabricated on the same substrate demonstrating Q of 2,900 in air at 473 MHz and a motional resistance of approximately 84 O. The highest Q of 4,300 was reported for a ring resonator at 230 MHz in air.; To further prove the commercial viability of such technology, ladder filters were realized out of arrays of contour-mode resonators. Intermediate frequency (IF) filters at 93 and 236 MHz were fabricated using rectangular plates and circular rings, respectively. (Abstract shortened by UMI.)...