High Frequency Strip-Type Solidly-Mounted Shear Mode Bulk Wave Resonator Using X-LT

Michio Kadota, Yoshimi Ishii, Shuji Tanaka

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The common materials of bulk acoustic wave (BAW) resonators are AlN and ScAlN. For a wider bandwidth, the Sc to Al ratio in ScAlN is increased up to 40%, but the Q factor often deteriorates and the impedance (Z) ratio does not improve significantly. For better filter performance, this study investigated monocrystalline LiTaO3 (LT) as a piezoelectric material for a high frequency strip type thickness shear mode (TS) solidly mounted resonator (SMR). We selected the SMR instead of a film BAW resonator (FBAR) with a cavity, because the suspended ultrathin LT plate is fragile. The strip type TS mode SMR is composed of two Al electrodes, a 2.0 µm thick X LT plate, an Al electrode, eight layers of SiO2 and Ta film (4+4 layers) and a 350 µm thick Si substrate from the top. The fabricated SMR shows a center frequency of 1 GHz, a bandwidth of 6.7% and an Z ratio of 62 dB. The temperature coefficients of frequency (TCF) at series and parallel resonance are as good as - 17 and -34 ppm/°C, respectively.

Original languageEnglish
Title of host publicationIUS 2020 - International Ultrasonics Symposium, Proceedings
PublisherIEEE Computer Society
ISBN (Electronic)9781728154480
DOIs
Publication statusPublished - 2020 Sep 7
Event2020 IEEE International Ultrasonics Symposium, IUS 2020 - Las Vegas, United States
Duration: 2020 Sep 72020 Sep 11

Publication series

NameIEEE International Ultrasonics Symposium, IUS
Volume2020-September
ISSN (Print)1948-5719
ISSN (Electronic)1948-5727

Conference

Conference2020 IEEE International Ultrasonics Symposium, IUS 2020
CountryUnited States
CityLas Vegas
Period20/9/720/9/11

Keywords

  • BAW resonator
  • GHz
  • Impedance ratio
  • SMR
  • Strip type shear mode
  • TCF
  • X LiTaO3

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

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