BAW resonators based on AlN with Ir electrodes for digital wireless transmissions

We investigate the performance of aluminum nitride (AlN)-based solidly mounted resonators (SMR) made with iridium (Ir) electrodes for applications in WCDMA filters. Ir/AlN/Ir stacks are grown on top of insulating Bragg mirrors composed of alternate lambda/4 layers of silicon oxycarbide (SiOC) and silicon nitride (Si₃N₄). We have developed the technological processes for the fabrication of filters including the trimming of the Ir top electrode for the tuning of the bandwidth. The influence of the thickness of the top electrode after the tuning process in the performance of the SMRs and filters is analyzed. The performance of the devices is compared with that of SMRs and filters of identical design made with Mo electrodes.