Temperature compensated surface acoustic wave devices with multiple buried mass loading strips
An acoustic wave device comprises a substrate including a piezoelectric material, interdigital transducer (IDT) electrodes disposed on a surface of the substrate, a first dielectric film having a lower surface disposed on the IDT electrodes and the surface of the substrate, first strips formed of a first material having a density greater than a density of the first dielectric film disposed within the first dielectric film over tips of the interdigitated electrode fingers in the edge regions of the IDT electrodes, and second strips formed of a second material having a density greater than the density of the first dielectric film disposed within the first dielectric film in the gap regions of the IDT electrodes, laterally spaced from the first strips in a direction perpendicular to a direction of propagation of a main acoustic wave through the acoustic wave device, and extending only partially over the gap regions.
1. An acoustic wave device comprising:
a substrate including a piezoelectric material;
interdigital transducer (IDT) electrodes including interdigitated electrode fingers disposed on a surface of the substrate, the IDT electrodes having gap regions, edge regions, and bus bar regions;
a first dielectric film having a lower surface disposed on the IDT electrodes and the surface of the substrate;
first strips formed of a first material having a density greater than a density of the first dielectric film disposed within the first dielectric film over tips of the interdigitated electrode fingers in the edge regions of the IDT electrodes; and
second strips formed of a second material having a density greater than the density of the first dielectric film disposed within the first dielectric film in the gap regions of the IDT electrodes, laterally spaced from the first strips in a direction perpendicular to a direction of propagation of a main acoustic wave through the acoustic wave device, and extending only partially over the gap regions to suppress high order spurious signals from being generated in the acoustic wave device.
2. The acoustic wave device of claim 1 wherein the first material is a same material as the second material.
3. The acoustic wave device of claim 1 wherein the first material and the second material are both metals.
4. The acoustic wave device of claim 3 wherein the first material and the second material are a same metal as a metal included in the IDT electrodes.
5. The acoustic wave device of claim 3 wherein the first material and the second material are different metals from a metal or metals included in the IDT electrodes.
6. The acoustic wave device of claim 4 wherein the first material and the second material are each dielectric materials.
7. The acoustic wave device of claim 1 wherein the second strips are narrower than the first strips.
8. The acoustic wave device of claim 7 wherein the second strips are laterally displaced from the first strips by a distance less than widths of the first strips.
9. The acoustic wave device of claim 8 wherein widths of the second strips are approximately the same as the distance.
10. The acoustic wave device of claim 1 wherein each of the first and second strips is disposed at a same height within the first dielectric film.
11. The acoustic wave device of claim 1 wherein the IDT electrodes further include min-bus bar electrodes and the second strips are disposed over the mini-bus bar electrodes.
12. The acoustic wave device of claim 1 further comprising third strips formed of a third material having a density greater than the density of the first dielectric film disposed within the first dielectric film in the gap regions of the IDT electrodes, laterally spaced from the first strips and from the second strips in a direction perpendicular to the direction of propagation of the main acoustic wave through the acoustic wave device, a sum of the widths of second strips and third strips being less than a width of the gap region.
13. The acoustic wave device of claim 12 further comprising fourth strips formed of a fourth material having a density greater than the density of the first dielectric film disposed within the first dielectric film in the gap regions of the IDT electrodes, laterally spaced from the first strips, the second strips, and the third strips in a direction perpendicular to the direction of propagation of the main acoustic wave through the acoustic wave device, a sum of the widths of second strips, third strips, and fourth strips being less than the width of the gap region.
14. The acoustic wave device of claim 13 wherein each of the first, second, third, and fourth materials is formed from a same material.
15. The acoustic wave device of claim 13 wherein the fourth strips have edges disposed at boundaries between the gap regions and the bus bar regions.
16. The acoustic wave device of claim 13 wherein each of the second, third, and fourth strips has a same width.
17. The acoustic wave device of claim 13 wherein each of the first, second, third, and fourth strips is laterally spaced from adjacent others of the first, second, third, and fourth strips by a same distance.
18. The acoustic wave device of claim 13 wherein at least two of the first, second, third, and fourth strips are disposed at a same height within the first dielectric film.
19. The acoustic wave device of claim 18 wherein each of the first, second, third, and fourth strips is disposed at a same height within the first dielectric film.
20. The acoustic wave device of any claim 1 further comprising a second dielectric film exhibiting a greater acoustic velocity than the first dielectric film disposed on the first dielectric film.
21. A radio frequency filter comprising as acoustic wave device of claim 1 .
22. An electronics module comprising the radio frequency filter of claim 21 .
23. An electronic device including the electronics module of claim 22 .