Development of RF FBAR devices for wireless applications

Abstract

Wireless communication systems appeared as a marvelous technology allowing for access to personal and other services, devices, computation and communication, wherever and whenever. Resonators and filters based on bulk acoustic waves (BAW) and surface acoustic waves (SAW) are widely used in wireless communication systems, from customer electronics to military systems, where frequency control is required. Day by day, customers are demanding higher speed and larger bandwidths, smaller in size but cheaper in price. In return, these trends necessitate the development of novel designing, structure techniques for the fabrication of devices with superior performance and higher capacity at lower manufacturing costs. ZnO-based film bulk acoustic resonator (FBAR) process has the excellent flexibility of choosing at film and/or combination, thereby it is compatible with IC technologies. This dissertation focuses on the designing and implementing techniques of microwave acoustic resonators for FBAR device applications. A prime choice of FBAR structure is ZnO-based solidly mounted resonator (SMR) type, which has been proved to have small size and great performance especially in power han-dling capability. ZnO-based FBARs are made of a thin film of piezoelectric material (ZnO) sandwiched between two metal electrodes. In order to prevent propagation of energy into the substrate, they are acoustically isolated from the substrate. In the case of SMR-type, ZnO layer is isolated from the substrate by a series of acoustic reflectors (Bragg reflectors). In applications, when an electric field is applied between the two electrodes, the piezoelectric material is deformed and an acoustic wave is propagated into the material bulk. A comprehensive manufacture process along with proposed techniques has been developed allowing the fabrication of high quality ZnO-based SMR-type FBAR device at the fundamental resonance frequency. The fabricated FBAR devices achieved very high retu...