This nano-acoustic resonator employs a ferroelectric transducer to enable the radio frequency (RF) front-end module necessary for the realization of 5G wireless communication networks. The majority of Americans today use a cellphone as a primary source for wireless communication. Each cellphone has at least 40-50 bulk acoustic resonator-based RF filters; these are used in Wi-Fi, GPS, Bluetooth, data/voice transceivers. In 2018, 440 million users subscribed to wireless carriers in the United States and this number keeps increasing. With the advent of the internet of things, more “smart” cars and household devices are communicating among themselves, and this requires our wireless networks to handle more users/devices at increasingly higher speeds. To prevent interference between devices and to increase data speed significantly, communication networks aim to scale the frequencies of certain wireless communication signals to extremely high frequencies in the millimeter wave (mm-wave) spectrum. In order to enable operation at mm-wave frequencies, the piezoelectric transducers used in the bulk acoustic resonator technology need to be miniaturized to sub-100nm thickness. Available thin-film resonator technology cannot achieve this thickness miniaturization because of their inherent material processing limitations such as nucleation, crystallization and texture development at such low thicknesses. Therefore, on scaling to the mm-wave frequency spectrum, the current piezoelectric films cannot preserve the critical electromechanical properties necessary for the effective operation of resonant devices.
Researchers at the University of Florida have developed a nano-acoustic resonator with a thin film ferroelectric transducer that exhibits superior piezoelectricity even at thicknesses less than 10 nm. This nanoscale resonator technology is capable of extreme frequency scaling, thus enabling 5G mm-wave wireless mobile systems.
Nano-acoustic resonator that achieves extreme frequency scaling for faster, clearer wireless communications
This nano-electro-mechanical (NEM) resonator creates monolithic cm- and mm-wave RF front ends and frequency references for 5G wireless communications systems. Resonators consist of a piezoelectric material in between two electrodes. The frequency of a bulk acoustic resonator is inversely proportional to its piezoelectric film thickness. For a resonator to operate in the mm-wave spectrum, the piezoelectric film thickness must be less than 100nm. This resonator uses an atomically engineered hafnium-zirconium oxide (Hf0.5Zr0.502) ferroelectric transducer. An atomic layer deposition process forms the Hf0.5Zr0.502 layer, ensuring better control of the thickness and uniformity of the film. This layer has a thickness in the range of 2nm to 20nm, well below the maximum thickness limit for mm-wave signal processing. Hf0.5Zr0.502 is already available in the current CMOS process material bank. Thus, with Hf0.5Zr0.502 transducer, this nano-acoustic resonator enables the first monolithic integration of acoustic frequency references/RF filters on chips operating in mm-wave bands.
