Bulk acoustic wave resonators, realized in piezoelectric thin films, are the major building block of the integrated filters used in portable wireless systems. These devices are realized through 2D patterning of piezoelectric films and operate in thickness-extensional resonance mode with a frequency defined by the film thickness. This architecture prohibits integration of multi-frequency filters on the same chip. Additionally, the 2D thickness-mode resonators does not sustain a good quality factor and power-handling when targeting higher operation frequencies in cm- and mm-wave regimes.

We are developing a 3D semiconductor-piezoelectric resonator architecture to address these fundamental limitations. This 3D resonator is based on integration of piezoelectric transducer on the sidewall of high aspect-ratio semiconductor fin, and is called the Fin Bulk Acoustic Resonator (FinBAR). FinBARs benefit from extreme frequency scaling, since their frequency is defined partially by semiconductor fin width. Additionally, they benefit from single-crystal semiconductor body with ultra-low dissipation and outstanding power-handing.

We have been developing different nodes if FinBAR technology, with a goal of further scaling the frequency to mm-wave. This effort has been followed by extensive work on fabrication process of these 3D resonators. Another pivotal aspect of moving to advanced nodes is development of super-thin piezoelectric transducers with high crystallinity on the sidewall.

The final goal of this research thrust is creating monolithically integrated arrays of filters to cover wide spectrum bands in cm- and mm-wave. The resulting chip-scale ultra-wideband spectral processor will revolutionize the wireless systems through enabling software-defined operation with very high spectrum-use efficiency.

This thrust has been followed since 2017 through projects sponsored by DARPA, NSF, and industry.

Featured Publications:

1. F. Hakim, T. Tharpe, and R. Tabrizian, “Ferroelectric-on-Si Super-High-Frequency Fin Bulk Acoustic Resonators with Hf_0.5Zr_0.5O₂ Nano-Laminated Transducers,” IEEE Microwave and Wireless Components Letters, vol. 31, no. 6, pp. 701-704, June 2021.
2. M. Ramezani, M. Ghatge, and R. Tabrizian, “High kt2.Q Silicon Fin Bulk Acoustic Resonators (FinBAR) for Chip-Scale Multi-Band Spectrum Analysis,” Proc. IEEE International Conference on Micro Electro Mechanical Systems (MEMS ‘18), pp. 158-161, January 2018.
3. M. Ramezani, M. Ghatge, and R. Tabrizian, “High-Q Silicon Fin Bulk Acoustic Resonators for Signal Processing beyond the UHF,” Proc. IEEE International Electron Device Meeting (IEDM ‘17), p. 40-1, December 2017.