US 12,113,509 B2
Acoustic wave device with IDT electrode including al metal layer and high acoustic impedance metal layer
Shou Nagatomo, Nagaokakyo (JP); and Katsuya Daimon, Nagaokakyo (JP)
Assigned to MURATA MANUFACTURING CO., LTD., Kyoto (JP)
Filed by Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed on Sep. 23, 2021, as Appl. No. 17/482,660.
Application 17/482,660 is a continuation of application No. PCT/JP2020/014839, filed on Mar. 31, 2020.
Claims priority of application No. 2019-071735 (JP), filed on Apr. 4, 2019.
Prior Publication US 2022/0014175 A1, Jan. 13, 2022
Int. Cl. H03H 9/25 (2006.01); H03H 9/02 (2006.01); H03H 9/145 (2006.01)
CPC H03H 9/25 (2013.01) [H03H 9/02559 (2013.01); H03H 9/02866 (2013.01); H03H 9/14541 (2013.01)] 18 Claims
OG exemplary drawing
 
1. An acoustic wave device comprising:
an energy confinement layer;
a piezoelectric layer on the energy confinement layer and made of Y-cut X-propagation lithium tantalate having a cut angle of equal to or more than about −10° and equal to or less than about 65°; and
an IDT electrode on the piezoelectric layer; wherein
the IDT electrode includes a plurality of electrode fingers, the plurality of electrode fingers including a multilayer body including an Al metal layer defined by an Al layer or an alloy layer including Al, and a high acoustic impedance metal layer that has a Young's modulus equal to or more than about 200 GPa and a higher acoustic impedance than an acoustic impedance of Al;
the high acoustic impedance metal layer is closer to the piezoelectric layer than the Al metal layer;
when a wavelength defined by an electrode finger pitch of the IDT electrode is denoted by λ and a wavelength specific film thickness of the piezoelectric layer is denoted by tLT, tLT≤1λ is satisfied; and
a total of normalized film thicknesses obtained by normalizing a film thickness of each layer of the plurality of electrode fingers by a density and a Young's modulus of the Al metal layer is denoted by T, the expression T≤0.1125tLT+0.0574 is satisfied.