Reduction of transverse leakage for SAW resonators on LiTaO<inf>3</inf> substrate

Abstract

This paper proposes a new structure to reduce the transverse SAW leakage for the SAW resonator on a 42° YX-LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrate. The leakage occurs from the inter-digital region toward the bus-bur region in the SAW resonators. The new structure has the Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> film on the outside of the interdigital region. In this structure, the SAW velocity in the bus-bur region becomes slower than the velocity in the inter-digital region. Therefore, the new structure could reduce the leakage, and contribute to confine the SAW energy in the inter-digital region. This structure is applied to the SAW resonator and the Ladder-type SAW filter fabricated on a 42° YX-LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrate. The insertion loss could be improved by reducing the transverse SAW leakage. This technique could be applied to the filters and duplexers using the leaky SAW on 42° YX-LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrate, and the SAW devices could exhibit the excellent performances.