Acoustic wave device
An acoustic wave device includes a support substrate, a piezoelectric layer on the support substrate and including a main surface, a cavity portion between the support substrate and the piezoelectric layer, an IDT electrode on the main surface and including first and second busbars, and first and second electrode fingers respectively connected to the first and second busbars, a wiring electrode on the main surface and connected to the IDT electrode, and a high thermal conductive film in the piezoelectric layer and having a thermal conductivity higher than a thermal conductivity of the piezoelectric layer. A portion of the IDT electrode is in a region overlapping the cavity portion, the high thermal conductive film is in a region overlapping the cavity portion, and at least one of the IDT electrode and the wiring electrode is connected to the high thermal conductive film directly or via a metal.
1 . An acoustic wave device comprising:
a support substrate;
a piezoelectric layer including lithium niobate or lithium tantalate on the support substrate in a thickness direction of the support substrate, and including a main surface in the first direction;
a cavity portion between the support substrate and the piezoelectric layer;
an IDT electrode on the main surface of the piezoelectric layer and including a first busbar and a second busbar that face each other, a plurality of first electrode fingers each including a base end connected to the first busbar, and a plurality of second electrode fingers each including a base end connected to the second busbar;
a wiring electrode on the main surface of the piezoelectric layer and connected to the IDT electrode; and
a high thermal conductive film in the piezoelectric layer in the thickness direction and having a thermal conductivity higher than a thermal conductivity of the piezoelectric layer; wherein
at least a portion of the IDT electrode is provided in a region overlapping the cavity portion in a plan view in the first direction;
the high thermal conductive film is provided in a region overlapping the cavity portion in a plan view in the first direction; and
the IDT electrode is connected to the high thermal conductive film directly or via a metal.
2 . The acoustic wave device according to claim 1 , wherein the high thermal conductive film includes at least one of alumina, silicon nitride, or aluminum nitride.
3 . The acoustic wave device according to claim 1 , wherein the high thermal conductive film includes silicon oxide.
4 . The acoustic wave device according to claim 1 , wherein the high thermal conductive film is also provided in a region that does not overlap the cavity portion in a plan view in the first direction.
5 . The acoustic wave device according to claim 1 , further comprising:
a through electrode penetrating the piezoelectric layer; wherein
the through electrode is in contact with the high thermal conductive film and at least one of the IDT electrode and the wiring electrode.
6 . The acoustic wave device according to claim 5 , wherein the through electrode penetrates the high thermal conductive film.
7 . The acoustic wave device according to claim 6 , further comprising:
a dielectric film between the support substrate and the piezoelectric layer; wherein
the through electrode is in contact with the dielectric film.
8 . The acoustic wave device according to claim 7 , wherein the dielectric film includes at least one of silicon oxide, silicon nitride, or alumina.
9 . The acoustic wave device according to claim 6 , wherein the through electrode is in contact with the support substrate.
10 . The acoustic wave device according to claim 1 , further comprising:
a side electrode on a surface of the piezoelectric layer parallel or substantially parallel to the thickness direction; wherein
the side electrode is in contact with the wiring electrode and the high thermal conductive film.
11 . The acoustic wave device according to claim 1 , wherein when a film thickness of the piezoelectric layer is defined as d, and a center-to-center distance between a first electrode finger of the plurality of first electrode fingers and a second electrode finger of the plurality of second electrode fingers adjacent to each other is defined as p, d/p≤about 0.5 is satisfied.
12 . The acoustic wave device according to claim 11 , wherein the acoustic wave device is structured to utilize bulk waves in a thickness-shear mode.
13 . The acoustic wave device according to claim 11 , wherein d/p is equal to or less than about 0.24.
14 . The acoustic wave device according to claim 11 , wherein when a region where the first electrode finger and the second electrode finger adjacent to each other overlap when viewed in a direction in which the first electrode finger and the second electrode finger adjacent to each other face each other is referred to as an excitation region, a metallization ratio of the plurality of first electrode fingers and the plurality of second electrode fingers with respect to the excitation region is defined as MR, MR≤about 1.75 (d/p)+0.075 is satisfied.
15 . The acoustic wave device according to claim 1 , wherein
Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate of the piezoelectric layer are within a range defined by Expression (1), Expression (2), or Expression (3):
(0°±10°,0° to 20°,arbitrary ψ) Expression (1);
(0°±10°,20° to 80°,0° to 60°(1−(θ−50) 2 /900) 1/2 ) or (0°±10°,20° to 80°,[180°−60°(1−(θ−50) 2 /900) 1/2 ] to 180°) Expression (2); and
(0°±10°,[180°−30°(1−(ψ−90) 2 /8100) 1/2 ] to 180°,arbitrary ψ) Expression (3).
16 . The acoustic wave device according to claim 1 , wherein the acoustic wave device is structured to utilize plate waves.
17 . The acoustic wave device according to claim 1 , wherein a thickness of the piezoelectric layer is equal to or more than about 50 nm and equal to or less than about 1000 nm.
18 . The acoustic wave device according to claim 1 , wherein a center-to-center distance between a first electrode finger of the plurality of first electrode fingers and a second electrode finger of the plurality of second electrode fingers adjacent to each other is equal to or more than about 1 μm and equal to or less than about 10 μm.
19 . The acoustic wave device according to claim 1 , wherein a width of each of the plurality of first electrode fingers and the plurality of second electrode fingers is equal to or more than about 150 nm and equal to or less than about 1000 nm.
20 . The acoustic wave device according to claim 1 , wherein the support substrate includes Si.