Acoustic wave device with multilayer interdigital transducer electrode
An acoustic wave device is disclosed. The acoustic waved device can be a shear horizontal mode surface acoustic wave device. The acoustic wave device can include a piezoelectric layer, an interdigital transducer electrode over the piezoelectric layer, and a temperature compensation layer over the interdigital transducer electrode. The piezoelectric layer can be a lithium niobate layer with a cut angle in a range of −20° YX to 25° YX. The interdigital transducer electrode includes a first layer having a first thickness and a second layer having a second thickness. The first layer affects acoustic properties of the acoustic wave device and the second layer affects electrical properties of the acoustic wave device. The first layer is positioned between the piezoelectric layer and the second layer. The first thickness is configured such that a frequency response of the acoustic wave device includes a Rayleigh mode response at a frequency higher than a shear horizontal mode response resonance. The first thickness can be greater than the second thickness.
1 . An acoustic wave device comprising:
a piezoelectric layer configured such that a shear horizontal mode is a main mode of the acoustic wave device;
an interdigital transducer electrode over the piezoelectric layer, the interdigital transducer electrode including a first layer having a first thickness and a second layer having a second thickness, the first layer affecting acoustic properties of the acoustic wave device and the second layer affecting electrical properties of the acoustic wave device, the first layer positioned between the piezoelectric layer and the second layer, the first thickness configured such that a frequency response of the acoustic wave device includes a Rayleigh mode response at a frequency higher than a shear horizontal mode response resonance; and
a temperature compensation layer over the interdigital transducer electrode.
2 . The acoustic wave device of claim 1 wherein the interdigital transducer electrode is configured such that the frequency response includes the Rayleigh mode response between a shear horizontal mode response resonance and a shear horizontal mode response anti-resonance.
3 . The acoustic wave device of claim 1 wherein the interdigital transducer electrode is configured to suppress transverse leakage of a surface acoustic wave generated by the acoustic wave device.
4 . The acoustic wave device of claim 1 wherein the first layer includes tungsten, molybdenum, platinum, iridium, gold, or copper, and the second layer includes aluminum.
5 . The acoustic wave device of claim 1 wherein the first thickness is greater than the second thickness.
6 . The acoustic wave device of claim 1 wherein the acoustic wave device is configured to generate a surface acoustic wave having a wavelength A, the first thickness is in a range of 0.02λ to 0.1λ.
7 . The acoustic wave device of claim 1 wherein the interdigital transducer electrode further comprising a third layer between the piezoelectric layer and the first layer.
8 . The acoustic wave device of claim 7 wherein the third layer is a titanium adhesion layer.
9 . The acoustic wave device of claim 1 wherein the temperature compensation layer is a silicon dioxide layer.
10 . The acoustic wave device of claim 1 further comprising a silicon nitride layer over the temperature compensation layer.
11 . The acoustic wave device of claim 10 wherein the interdigital transducer electrode includes a bus bar region, an active region that includes a center region and an edge region, and a gap region between the bus bar region and the edge region, the silicon nitride layer is disposed over the center region of the interdigital transducer electrode.
12 . The acoustic wave device of claim 11 wherein the silicon nitride layer is disposed over at least a portion of the edge region of the interdigital transducer electrode, and portions of the temperature compensation layer over the edge region and the bus bar region are uncovered by the silicon nitride layer.
13 . The acoustic wave device of claim 1 wherein the interdigital transducer electrode further comprises a hammer head structure.
14 . The acoustic wave device of claim 1 wherein the interdigital transducer electrode further comprises a dummy finger disposed in a gap region between a bus bar and an active region.
15 . The acoustic wave device of claim 14 wherein a width of a finger of the interdigital transducer electrode in the gap region and a width of the dummy finger are narrower than a width of the finger in the active region.
16 . The acoustic wave device of claim 1 wherein the piezoelectric layer is a lithium niobate layer having a cut angle in a range of −20° YX to 25° YX.
17 . A shear horizontal acoustic wave device comprising:
a lithium niobate piezoelectric layer having a cut angle in a range of −20° YX to 25° YX and configured such that a shear horizontal mode is a main mode of the acoustic wave device;
an interdigital transducer electrode over the piezoelectric layer, the interdigital transducer electrode including a first layer having a first thickness and a second layer having a second thickness, a material of the first layer being more dense than a material of the second layer, the first layer positioned between the piezoelectric layer and the second layer, the first thickness being greater than the second thickness and is configured such that a frequency response of the acoustic wave device includes a Rayleigh mode response at a frequency higher than a shear horizontal mode response resonance; and
a temperature compensation layer over the interdigital transducer electrode.
18 . The shear horizontal acoustic wave device of claim 17 wherein the interdigital transducer electrode is configured to suppress transverse leakage of a surface acoustic wave generated by the acoustic wave device.
19 . An acoustic wave device comprising:
a lithium niobate piezoelectric layer having a cut angle in a range of −20° YX to 25° YX such that a shear horizontal mode is a main mode of the acoustic wave device;
an interdigital transducer electrode over the piezoelectric layer, the interdigital transducer electrode including a tungsten layer having a first thickness and an aluminum layer having a second thickness, the tungsten layer positioned between the lithium niobate piezoelectric layer and the aluminum layer, the first thickness configured such that a frequency response of the acoustic wave device includes a Rayleigh mode response at a frequency higher than a shear horizontal mode response; and
a temperature compensation layer over the interdigital transducer electrode.
20 . The acoustic wave device of claim 19 wherein the acoustic wave device is configured to generate a surface acoustic wave having a wavelength A, the first thickness is at least 0.06λ.