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US-12620960-B2 - Complementary switchable dual-mode bulk acoustic wave resonator and filter

US12620960B2US 12620960 B2US12620960 B2US 12620960B2US-12620960-B2

Abstract

A laminated Sc x Al 1-x N BAW resonator with complementary-switchable operation in thickness extensional modes (TE l and TE N ). The resonator comprises ferroelectric Sc x Al 1-x N layers alternatively stacked with metal electrodes, enabling independent polarization switching of each piezoelectric layer. Opting for unanimous or alternative poling of the Sc x Al 1-x N layers, the resonator can be switched to operate in two complementary states with either TE l or TE N active resonance modes of similarly large k t 2 .

Inventors

  • Roozbeh Tabrizian
  • Dicheng Mo
  • Shaurya Dabas
  • Sushant Rassay

Assignees

  • UNIVERSITY OF FLORIDA RESEARCH FOUNDATION, INCORPORATED

Dates

Publication Date
20260505
Application Date
20230626

Claims (19)

  1. 1 . A bulk acoustic wave resonator comprising: a silicon substrate; an aluminum nitride (AlN) layer deposited on the silicon substrate; and a stack comprising a plurality of ferroelectric scandium-aluminum nitride (ScAlN) layers that are alternatively stacked between a plurality of molybdenum (Mo) electrode layers, wherein the plurality of ScAlN layers comprise independent switchability of polarization.
  2. 2 . The bulk acoustic wave resonator of claim 1 further comprising a radio frequency (RF) port and one or more direct current ports, wherein the one or more direct current ports are configured for independent polarization control of the plurality of ScAlN layers.
  3. 3 . The bulk acoustic wave resonator of claim 1 further comprising intrinsic switchability between a first thickness mode and a second thickness mode based on poling of the plurality of ScAlN layers in same or opposite directions.
  4. 4 . The bulk acoustic wave resonator of claim 1 further comprising a self-ovenization component configured to reduce switching voltage.
  5. 5 . The bulk acoustic wave resonator of claim 4 , wherein the self-ovenization component comprises a direct current-biased serpentine-shaped top electrode.
  6. 6 . The bulk acoustic wave resonator of claim 1 further comprising operation in on and off states based on polarization alignment of the plurality of ScAlN layers in same or opposite directions.
  7. 7 . The bulk acoustic wave resonator of claim 1 , wherein the plurality of ScAlN layers are deposited using reactive magnetron sputtering from segmented scandium-aluminum targets.
  8. 8 . The bulk acoustic wave resonator of claim 1 , wherein the plurality of Mo electrode layers are deposited using direct current sputtering.
  9. 9 . The bulk acoustic wave resonator of claim 1 , wherein a bottom one of the plurality of Mo electrode layers is patterned using boron trichloride (BCl3) gas in an inductively coupled plasma reactive-ion-etching system.
  10. 10 . The bulk acoustic wave resonator of claim 1 , wherein a bottom Mo electrode layer of the plurality of Mo electrode layers comprises a bottom Mo electrode patterned using tapered photoresist mask features created by proximity exposure mode photolithography.
  11. 11 . The bulk acoustic wave resonator of claim 1 , wherein one or more of the plurality of Mo electrode layers include slanted sidewalls.
  12. 12 . The bulk acoustic wave resonator of claim 1 , wherein a top one of the plurality of Mo electrode layers comprises a top Mo electrode patterned using a photoresist mask created in contact mode lithography.
  13. 13 . The bulk acoustic wave resonator of claim 1 , wherein the plurality of ScAlN layers are etched using a timed chlorine-hydrogen (Cl 2 —H 2 ) based recipe.
  14. 14 . The bulk acoustic wave resonator of claim 1 , wherein the plurality of ScAlN layers are configured to switch operation via application of a corresponding plurality of pulse signals.
  15. 15 . The bulk acoustic wave resonator of claim 1 further comprising a first state including a first thickness-extensional mode that operates at approximately 7 GHz and a second state including a second thickness-extensional mode that operates at approximately 13 GHz.
  16. 16 . The bulk acoustic wave resonator of claim 1 further comprising complementary switchable operation between a first operation state and a second operation state.
  17. 17 . The bulk acoustic wave resonator of claim 16 , wherein the first operation state comprises unanimous polarization direction in the plurality of ScAlN layers.
  18. 18 . The bulk acoustic wave resonator of claim 16 , wherein the second operation state comprises alternative polarization switching of the plurality of ScAlN layers.
  19. 19 . The bulk acoustic wave resonator of claim 16 , wherein a frequency ration of the first operation state and the second operation state is based on a thickness of the AlN layer or the plurality of Mo electrode layers.

Description

CROSS REFERENCE TO RELATED APPLICATION This application claims the priority of U.S. Provisional Application No. 63/367,255, entitled “COMPLEMENTARY SWITCHABLE DUAL-MODE BULK ACOUSTIC WAVE RESONATOR AND FILTER,” filed on Jun. 29, 2022, the disclosure of which is hereby incorporated by reference in its entirety. GOVERNMENT SUPPORT This invention was made with government support under Agreement No. HR0011-20-9-0049, awarded by DARPA. The government has certain rights in the invention. TECHNICAL FIELD The present application relates to a bulk acoustic wave resonator, and more particularly to a bulk acoustic wave resonator with complementary switchable operation. BACKGROUND With the ever-rising increase in wireless data traffic, adaptive spectrum allocation becomes increasingly vital to avoid congestion and interference. Realization of adaptive spectrum allocation in wireless systems requires reconfigurable spectral processors that enable dynamic control over pass- and stop-bands at the radio frequency front-end (RFFE). Currently, integrated radio frequency (RF) duplexers and filters are created using aluminum nitride (AlN) surface and bulk acoustic wave (S/BAW) resonators. High quality-factor (Q) AlN BAW and SAW filter technologies with frequencies as high as 6 GHz are extensively adopted in RFFE of modern wireless systems. These technologies, however, do not provide any intrinsic frequency tunability or switchability, and their operation is limited to a fixed band. Therefore, extension of communication capacity, to enhance data rates and exploit uncongested spectrum in centimeter (cm)- and millimeter (mm)-wave regimes, may require arraying a large set of fixed-frequency filters using external switches to enable band selection and data aggregation. This strategy is not scalable considering the unfavorable increase in RFFE footprint with the addition of new filters, and excessive loss and power consumption of multiplexers needed for switching. As an alternative, existing acoustic resonator technologies can achieve intrinsic configurability based on the use of perovskite ferroelectric and paraelectric transducers. In these technologies the dependence of transducer polarization and acoustic velocity on direct current (DC) electric field enables intrinsic switching and frequency tuning of the resonator. However, the major limitation of existing acoustic resonator technologies is their frequency scaling beyond the ultra-high-frequency regime (UHF: 0.3-3 GHz). This is due to the excessive electrical and mechanical loss of conventional perovskite and ferroelectric films and the processing challenges with thickness miniaturization upon extreme frequency scaling of the resonators. BRIEF SUMMARY Various embodiments described herein relate to laminated ScxAl1-xN BAW resonators with complementary switchable operation in first and second thickness extensional modes. In some embodiments, two ferroelectric scandium-aluminum nitride (ScxAl1-xN) layers are alternatively stacked with three molybdenum (Mo) electrode layers, to create a laminated ScxAl1-xN BAW resonator with independent switchability of polarization in constituent transducers. A laminated ScxAl1-xN BAW resonator may include intrinsic switchability between first and second thickness modes, when the ScxAl1-xN layers are poled in the same or opposite directions, respectively. According to one embodiment, a laminated ScxAl1-xN BAW resonator comprises alternative stacking of two Sc0.28Al0.72N layers with three Mo electrode layers, enabling tailorability of transducer polarization across the thickness. In some embodiments, the laminated ScxAl1-xN BAW resonator may comprise an intrinsically switchable thickness-extensional ScxAl1-xN BAW resonator including self-ovenization to reduce switching voltage. Upon aligning the polarization of the two Sc0.28Al0.72N layers in the same or opposite directions, the electromechanical coupling of the thickness-extensional mode may be maximized or nulled, resulting in operation of the resonator in “on” and “off” states, respectively. The switching voltage may be significantly reduced by self-ovenization of the resonator through a DC-biased serpentine-shaped top electrode and due to a temperature-dependent reduction in Sc0.28Al0.72N coercive field. According to one embodiment, a bulk acoustic wave resonator comprises a silicon substrate, an aluminum nitride layer deposited on the silicon substrate, and a stack comprising ferroelectric scandium-aluminum nitride layers alternatively stacked between molybdenum electrode layers. In some embodiments, the bulk acoustic wave resonator further comprises independent switchability of polarization. In some embodiments, the bulk acoustic wave resonator further comprises intrinsic switchability between first and second thickness modes based on poling of the ScAlN layers in same or opposite directions. In some embodiments, the bulk acoustic wave resonator further comprises a self-ovenization component