RF Passive Components Based on Aluminum Nitride Cross-Sectional Lamé-Mode MEMS Resonators

Abstract

This paper presents a new class of monolithic integrated RF passive components based on the recently developed aluminum nitride (AlN) MEMS cross-sectional Lame-mode resonator (CLMR) technology. First, we experimentally demonstrate a 920-MHz CLMR showing the values of electromechanical coupling coefficient ( $k_{t}^{\mathbf {2}}$ ) and quality factor ( $Q_{\mathrm{ load}}$ ) in excess of 6.2% and 1750, respectively. To the best our knowledge, the resulting figure of merit ( $= Q\cdot k_{t}^{2}$ ), in excess of 108, is the highest ever reported for AlN-based piezoelectric resonators using interdigitated metallic electrodes (IDTs) and operating in the same frequency range. Second, we report the measured performance of an 870-MHz ladder filter, synthesized using three degenerate CLMRs. This device shows the values of fractional bandwidth (BW $_{3\,\text {dB}}$ ) in excess of 3.8% and an insertion loss of ~1.5 dB. Finally, we report the performance of the first piezoelectric transformer (PT) based on the CLMR technology. This device, dubbed “cross-sectional Lame-mode transformer,” exploits the high- $\text{k}_{t}^{\mathbf {2}}$ of the CLMR technology to achieve high values of open-circuit voltage-gains ( $G_{v}$ ) in excess of 39. To the best of our knowledge, such a high $G_{v}$ -value is the highest ever reported for MEMS-based PTs operating in the microwave frequency range.