Acoustic wave device with transverse mode suppression
Aspects of this disclosure relate to an acoustic wave device with transverse mode suppression. The acoustic wave device can include a piezoelectric layer, an interdigital transducer electrode, a temperature compensation layer, and a multi-layer mass loading strip. The mass loading strip has a density that is higher than a density of the temperature compensation layer. The mass loading strip can overlap edge portions of fingers of the interdigital transducer electrode. The mass loading strip can include a first layer for adhesion and a second layer for mass loading. The mass loading strip can suppress a transverse mode.
1. An acoustic wave device comprising a multi-layer mass loading strip at least partially overlapping edge portions of a plurality of fingers of an interdigital transducer electrode, the multi-layer mass loading strip having a mass sufficient to suppress at least a portion of a transverse mode, the multi-layer mass loading strip including a first layer and a second layer, the first layer of the multi-layer mass loading strip positioned between the second layer of the multi-layer mass loading strip and the interdigital transducer electrode, and the first layer improves crystal orientation of the second layer.
2. The acoustic wave device of claim 1 wherein the second layer of the multi-layer mass loading strip has a higher mass than the first layer of the multi-layer mass loading strip.
3. The acoustic wave device of claim 1 wherein the second layer of the multi-layer mass loading strip is a conductive strip.
4. The acoustic wave device of claim 1 wherein the first layer of the multi-layer mass loading strip includes titanium.
5. The acoustic wave device of claim 1 wherein the first layer of the multi-layer mass loading strip is an adhesion layer that improves the crystal orientation of the second layer.
6. The acoustic wave device of claim 5 wherein the second layer of the multi-layer mass loading strip includes molybdenum.
7. The acoustic wave device of claim 1 wherein the acoustic wave device is configured to generate a surface acoustic wave.
8. The acoustic wave device of claim 1 wherein the second layer of the multi-layer mass loading strip has a higher density than a density of the interdigital transducer electrode.
9. The acoustic wave device of claim 1 wherein the multi-layer mass loading strip includes a third layer that is an adhesion layer that adheres to a temperature compensation layer.
10. The acoustic wave device of claim 1 wherein the first layer of the multi-layer mass loading strip is spaced apart from a piezoelectric layer.
11. A method of filtering a radio frequency signal, the method comprising:
receiving the radio frequency signal at an input port of an acoustic wave filter that includes an acoustic wave resonator, the acoustic wave resonator including a multi-layer mass loading strip at least partially overlapping edge portions of fingers of an interdigital transducer electrode, the multi-layer mass loading strip including a first layer and a second layer, the first layer of the multi-layer mass loading strip positioned between the second layer of the multi-layer mass loading strip and the interdigital transducer electrode, and the first layer improves crystal orientation of the second layer; and
filtering the radio frequency signal with the acoustic wave filter, the filtering including suppressing a transverse mode using the multi-layer mass loading strip of the acoustic wave resonator.
12. The method of claim 11 further comprising forming the second layer of the multi-layer mass loading strip with a higher mass than the first layer of the multi-layer mass loading strip.
13. The method of claim 11 further comprising forming the second layer of the multi-layer mass loading strip as a conductive strip.
14. The method of claim 11 further comprising forming the first layer of the multi-layer mass loading strip to include titanium.
15. The method of claim 11 wherein the first layer of the multi-layer mass loading strip improves the crystal orientation of the second layer.
16. The method of claim 15 wherein the second layer of the multi-layer mass loading strip includes molybdenum.
17. The method of claim 11 wherein the acoustic wave resonator generates a surface acoustic wave.
18. The method of claim 11 further comprising forming the second layer of the multi-layer mass loading strip to have a higher density than a density of the interdigital transducer electrode.
19. The method of claim 11 further comprising forming a third layer on of the multi-layer mass loading strip that adheres to a temperature compensation layer.
20. The method of claim 11 further comprising spacing the first layer of the multi-layer mass loading strip apart from a piezoelectric layer.