3-GHz BAW composite resonators integrated with CMOS in a single-chip configuration

This work presents the design and characterization for composite Aluminum Nitride on Silicon based thin Film Bulk Acoustic Wave Resonators (c-FBAR) fabricated using a proprietary InvenSense AlN-MEMS + CMOS process. High performance pentagon shaped resonators are fabricated and operated under a high-order thickness-extensional mode with an electromechanical coupling coefficient of 2.21% and an unloaded quality factor of ~1,933 at 3.26 GHz. Detailed de-embedding is performed to remove the parasitic elements which would degrade the resonator performance in the GHz operational frequency range. After de-embedding, motional resistance of 1.5 Ω is recorded. Such an InvenSense platform allows us to realize MEMS + CMOS integrated systems where an inverter based Pierce oscillator with power consumption of 0.5 mW at 1.1V bias is designed. However, insufficient performance of the MEMS resonator impedes the oscillator implementation. The circuit has an active area of 55×85 μm2 and overall CMOS-MEMS integrated area is about 300×250 μm2.