TECHNICAL FIELD

The present application relates to acoustic resonators, in particular, to hafnium-zirconium oxide-based piezoelectric transducers for nano-electromechanical systems.

BACKGROUND

Ever since the advent of micro and nano-electro-mechanical resonators, the need for large electromechanical coupling coefficient, extreme frequency scalability, and CMOS processing compatibility have been the governing drivers for the advancement of thin-film piezoelectric transducers. The development of high quality piezoelectric films has enabled high-performance bulk acoustic resonators and filters which are employed in RF front-end modules for wireless mobile systems.

However, the forthcoming 5G era, with the ambitious target of the extending wireless communication to the mm-wave regime, has raised an unprecedented urgency for transformation of piezoelectric films and acoustic resonator architectures. To fulfill the demand for extreme frequency scaling to mm-wave regime, the quest for material and architectural improvements of the acoustic resonator technology continues. While the development of fin-based resonator architectures and the use of single crystal films and substrates help further the scaling limits beyond the current state, the ultimate bound of the frequency scaling is set by the technological limitations in piezoelectric film thickness miniaturization. Because the frequencies of bulk acoustic resonators are inversely proportional to the thickness of the piezoelectric film, extreme frequency scaling to mm-wave regime requires radical thickness miniaturization to sub-100 nm range. Such a miniaturization is substantially inhibited by the size requirements of nucleation, crystallization, and texture development processes in current piezoelectric film deposition techniques (e.g. Magnetron-Sputtering and Metalorganic Vapor-Phase Epitaxy or MOCVD), which drastically degrade the electromechanical coupling and energy dissipation coefficients.

A scaled sub-100 nm thickness piezoelectric resonator fabricated with CMOS compatible techniques is needed to address this technological gap.

BRIEF SUMMARY

Embodiments of the current disclosure provide a two-port acoustic resonator, comprising: a substrate, a first aluminum nitride (AlN) layer on the substrate; a first molybdenum (Moly) layer disposed on the first AlN layer; a first transducer formed on the first Moly layer, wherein the first transducer comprises, a second AlN layer disposed on the first Moly layer; a second Moly layer disposed on the second AlN layer; and a second transducer formed on the second Moly layer wherein the second transducer comprises, a hafnium zirconium oxide (HZO) layer disposed on the second Moly layer; a titanium nitride (TiN) layer disposed on the HZO layer; and a first conductive layer disposed on the TiN layer; wherein the second transducer is located in the vicinity of the first transducer.

Optionally, the HZO layer is formed by applying atomic layer deposition (ALD).

Optionally, the HZO layer has a thickness ranging from 2 nm to 20 nm.

Optionally, the first and the second conductive layers include one of platinum (Pt), aluminum (Al), gold (Au), and silver (Ag).

Optionally, the first AlN layer is a seed layer and the second AlN layer is a c-axis oriented crystalline layer, and have a thickness ranging from 50 nm to 5 um.

Optionally, the substrate is a SOI having a device layer on a BOX layer.

Embodiments of the current disclosure provide a one-port acoustic resonator, including: a substrate; a first conductive layer disposed on the substrate; a first titanium nitride (TiN) layer disposed on the first conductive layer; a one-port transducer formed on the first TiN layer, wherein the one-port transducer comprises: an HZO layer disposed on the first TiN layer; a molybdenum (Moly) layer disposed on the HZO layer; a second TiN layer disposed on the Moly layer; and a second conductive layer disposed on the second TiN layer.

Embodiments of the current disclosure provide a method of fabricating the one-port acoustic resonator, comprising, providing the substrate; depositing the first conductive layer on the substrate; depositing the first TiN layer on the first conductive layer; depositing the HZO layer on the first TiN layer; depositing the Moly layer on the HZO layer; depositing the second TiN layer on the HZO layer; depositing the second conductive layer on the second TiN layer; patterning the second conductive layer, the second TiN layer and the HZO layer to form the one-port transducer; and releasing the one-port acoustic resonator by etching a trench around and removing the substrate.

Optionally, the HZO layer is deposited by applying atomic layer deposition (ALD).

Embodiments of the current disclosure also provide a method of fabricating a two-port acoustic resonator, including: providing a silicon-on-insulator substrate; depositing a first aluminum nitride (AlN) layer on the substrate, wherein the first AlN layer is a seed layer; depositing a first molybdenum (Moly) layer on the first AlN layer; depositing a second AlN layer on the first Moly layer; depositing a second Moly layer on the second AlN layer; patterning the second Moly layer to define a first transducer; using atomic layer deposition to deposit a first hafnium zirconium oxide (HZO) layer on the second Moly layer; depositing a first titanium nitride (TiN) layer on the first HZO layer; depositing a first conductive film on the first TiN layer; patterning the first conductive layer, the first TiN layer and the first HZO layer to form the second transducer; patterning and depositing a second conductive layer on the second transducer; and releasing the two-port acoustic resonator by etching a trench around and removing the substrate.

