CMOS-Based Fluorite Ferroelectrics: Enabling Microwave Acoustic Resonators for On-Chip Frequency Control

Access to nanoscale piezoelectric transducers in advanced semiconductor processes enables realization of acoustic resonators on CMOS chips. Monolithically integrated acoustic resonators facilitate the creation of on-chip clocks, local oscillators, and filters with improved performance, size, and cost. The discovery of ferroelectricity in fluorite-structured oxides, such as hafnia and zirconia, has augured the emergence of the long-coveted CMOS piezoelectric transducer. Atomic-layer-deposited hafnia-zirconia are already used, in amorphous form, as high-k dielectrics in advanced semiconductor nodes. Once subjected to proper atomic engineering, these fluorites can take polar crystalline forms with large piezoelectric coupling that enables creation of high-performance acoustic resonators. In this talk, I will present an overview of CMOS-based fluorite ferroelectrics and their properties pertaining to acoustic resonator performance merits. I will introduce our efforts in (1) developing hafnia-zirconia piezoelectric transducers for creation of super-high-frequency acoustic resonators with high electromechanical-coupling and quality-factor, and intrinsic switchability, (2) development of three-dimensional acoustic resonator technology based on integrating hafnia-zirconia on semiconductor fins, enabling massive integration of multi-band filter arrays and wideband switch-free multiplexers, and (3) development of ultra-stable oscillators using temperature-compensated hafnia-zirconia resonators.