High-Q UHF and SHF Bulk Acoustic Wave Resonators with Ten-Nanometer Hf0.5Zr0.5O2 Ferroelectric Transducer

This paper reports the use of 10nm ferroelectric hafnium-zirconium-oxide (Hf
_0.5
Zr
_0.5
O
₂
) transducers for implementation of high quality-factor (Q) bulk acoustic wave (BAW) resonators over ultra- and super-high-frequency regimes. Atomic layer deposited Hf
_0.5
Zr
_0.5
O
₂
film is engineered through layering and thermo-mechanical treatment to promote dominant growth of non-centrosymmetric orthorhombic texture with large ferroelectric properties. The 10nm ferroelectric Hf
_0.5
Zr
_0.5
O
₂
film along with 120nm magnetron-sputtered aluminum nitride piezoelectric film are used to create two-port multi-morph resonators operating in in-plane and out-of-plane BAW modes. Resonators with frequencies (f
₀
) over 38 MHz - 13 GHz are demonstrated with Qs over 400-900. Among these, the 12.84 GHz thickness-extensional BAW resonator shows a record-high f
₀
×Q of ~3.9×10
¹²
, highlighting the potential of atomically thin Hf
_0.5
Zr
_0.5
O
₂
ferroelectric films for realization of integrated frequency references and spectral processors in cm- and mm-wave regimes for emerging 5G wireless systems.