A High Quality Factor, 19-GHz Periodically Poled AlScN BAW Resonator Fabricated in a Commercial XBAW Process
Izhar Izhar, Merrilyn Mercy Adzo Fiagbenu, Xingyu Du, Pariasadat Musavigharavi, Yang Deng, Akhil Gunda, Jeff Leathersich, Craig Moe, Abhay Kochhar, Eric A. Stach, Ramakrishna Vetury, Roy H. Olsson
Abstract
This article presents 19-GHz bulk acoustic wave (BAW) resonators realized in a periodically poled piezoelectric film (P3F) microfabricated in a commercial XBAW process. The polarization of the three layers comprising the P3F film are realized via a combination of as-grown (two-layer) and electrically poled (one-layer) aluminum scandium nitride (AlScN). To improve the series (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{s}$ </tex-math></inline-formula>) and maximum (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\max }$ </tex-math></inline-formula>) quality factors, the device is constructed by connecting two-BAW resonators in series, which lowers the effect of the via resistance when compared with a traditional single BAW. Resonators achieved <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\max }$ </tex-math></inline-formula> of 531 (with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{s}$ </tex-math></inline-formula> of 348 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{p}$ </tex-math></inline-formula> of 264) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text {FoM}}_{{os}}$ </tex-math></inline-formula> (defined as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text {FoM}}_{{os}} = {{f}_{{s},{p}} {Q}}_{{s},{p}} \times {{10}}^{-{9}}$ </tex-math></inline-formula>, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{{s},{p}}$ </tex-math></inline-formula> is the quality factor at series (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}_{s}$ </tex-math></inline-formula>) or parallel (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}_{p}$ </tex-math></inline-formula>) resonance frequency) of 6542 at 18.8-GHz frequency, which is higher than most of the state-of-the-art piezoelectric BAW resonators operating at similar and higher frequencies. The experimental results indicate that the P3F BAW resonators are promising for applications in emerging RF communication systems.