Design, fabrication and characterization of Bulk Acoustic Wave Resonators

Abstract

The constant demand for higher speed and larger bandwidths together with the massive development of personal communications systems, navigation, satellite communications as well as personal computer and data processing systems have driven fabrication technology to its limits. This, in turn, necessitates the development of novel functional materials for the fabrication of devices with superior performance and higher capacity at reduced manufacturing costs. Researches have been paying attention to ferroelectric materials, such as barium strontium titanate (BST), because of their eld-induced piezoelectric property. They are able to produce a voltage that is proportional to whatever mechanical pressure is applied. This property gives these types of ferroelectric materials the ability to be switchable and tunable in the presence of an electric eld. Sensors, non-volatile memory and DRAMs and pyroelectric detectors are few of many applications where these ferroelectic materials are used thanks to these features. Ferroelectric bulk acoustic wave (BAW) resonators and lters that are switchable and tunable promise to reduce the size and complexity of many devices. This dissertation presents the design, fabrication and experimental evaluation of thin lm bulk acoustic wave (BAW) resonators and the characterization of some steps in between. The BAW resonators in this work were fabricated on silicon substrates as solidly mounted resonator (SMR) structure with number of periodic layers of silicon dioxide and tantalum oxide as a Bragg re ector in order to acoustically isolate the resonator from the damping e ect of the substrate, enhancing the quality factor. 1