Multilayer piezoelectric substrate for acoustic wave device
A surface acoustic wave device has a piezoelectric substrate having a cut angle (e.g., the piezoelectric angle is cut so as to have a crystal orientation) that allows the surface acoustic wave device to operate as a longitudinally leaky surface acoustic wave device that confines the acoustic wave energy within the piezoelectric substrate and that has less propagation attenuation and a higher electromechanical coupling coefficient k 2 .
1. A surface acoustic wave device comprising:
an interdigital transducer electrode including a plurality of fingers;
a piezoelectric layer of lithium niobate disposed below the interdigital transducer electrode, the piezoelectric layer having a cut angle defined by first, second and third Euler angles (ϕ 1 , θ 1 , ψ 1 ) so that the second Euler angle θ 1 has a value of about 76<θ 1 <86 degrees, the piezoelectric layer having a height H1 with a value of about 0.3 L<H1<0.9 L, where L is a pitch between the plurality of fingers of the interdigital transducer electrode; and
a support substrate layer disposed below the piezoelectric layer.
2. The surface acoustic wave device of claim 1 wherein the support substrate layer is made of a material chosen from a group consisting of quartz, silicon and diamond.
3. The surface acoustic wave device of claim 2 wherein the support substrate layer has a cut angle defined by first, second and third Euler angles (ϕ 2 , θ 2 , ψ 2 ) so that the second Euler angle θ 2 has a value of about 25<θ 2 <70 degrees.
4. The surface acoustic wave device of claim 3 wherein the first Euler angle ϕ 1 of the support substrate layer is 0 degrees and the third Euler angle ψ 2 of the support substrate layer is 90 degrees.
5. The surface acoustic wave device of claim 1 wherein the first Euler angle ϕ 1 of the piezoelectric layer is 0 degrees and the third Euler angle ψ 1 of the piezoelectric layer is 90 degrees.
6. The surface acoustic wave device of claim 1 further including a functional layer between the piezoelectric layer and the support substrate layer.
7. The surface acoustic wave device of claim 6 wherein the functional layer is a silicon dioxide layer having a thickness H2 with a value of about 0.3 L<H2<0.7 L, where L is a pitch between the plurality of fingers of the interdigital transducer electrode.
8. A radio frequency module comprising:
a package substrate;
a surface acoustic wave resonator configured to filter a radio frequency signal, the surface acoustic wave resonator including an interdigital transducer electrode including a plurality of fingers, a piezoelectric layer of lithium niobate disposed below the interdigital transducer electrode, the piezoelectric layer having a cut angle defined by first, second and third Euler angles (ϕ 1 , θ 1 , ψ 1 ) so that the second Euler angle θ 1 has a value of about 76<θ 1 <86 degrees, and a support substrate layer disposed below the piezoelectric layer, the piezoelectric layer having a height H1 with a value of about 0.3 L<H1<0.9 L, where L is a pitch between the plurality of fingers of the interdigital transducer electrode; and
additional circuitry, the surface acoustic wave resonator and additional circuitry disposed on the package substrate.
9. The radio frequency module of claim 8 wherein the support substrate layer is made of quartz.
10. The radio frequency module of claim 9 wherein the support substrate layer has a cut angle defined by first, second and third Euler angles (ϕ 2 , θ 2 , ψ 2 ) so that the second Euler angle θ 2 has a value of about 25<θ 2 <70 degrees.
11. The radio frequency module of claim 10 wherein the first Euler angle ϕ 1 of the support substrate layer is 0 degrees and the third Euler angle ψ 2 of the support substrate layer is 90 degrees.
12. The radio frequency module of claim 8 wherein the first Euler angle ϕ 1 of the piezoelectric layer is 0 degrees and the third Euler angle ψ 1 of the piezoelectric layer is 90 degrees.
13. The radio frequency module of claim 8 further including a functional layer between the piezoelectric layer and the support substrate layer.
14. The radio frequency module of claim 13 wherein the functional layer is a silicon dioxide layer having a thickness H2 with a value of about 0.3 L<H2<0.7 L, where L is a pitch between the plurality of fingers of the interdigital transducer electrode.
15. A wireless communication device comprising:
an antenna; and
a front end module including one or more surface acoustic wave resonators configured to filter a radio frequency signal associated with the antenna, each surface of the one or more acoustic wave resonators including an interdigital transducer electrode including a plurality of fingers, a piezoelectric layer of lithium niobate disposed below the interdigital transducer electrode, the piezoelectric layer having a cut angle defined by first, second and third Euler angles (ϕ 1 , θ 1 , ψ 1 ) so that the second Euler angle θ 1 has a value of about 76<θ 1 <86 degrees, and a support substrate layer disposed below the piezoelectric layer, the piezoelectric layer having a height H1 with a value of about 0.3 L<H1<0.9 L, where L is a pitch between the plurality of fingers of the interdigital transducer electrode.
16. The wireless communication device of claim 15 wherein the first Euler angle ϕ 1 of the piezoelectric layer is 0 degrees and the third Euler angle vi of the piezoelectric layer is 90 degrees.
17. The wireless communication device of claim 15 wherein the support substrate layer has a cut angle defined by first, second and third Euler angles (ϕ 2 , θ 2 , ψ 2 ) so that the second Euler angle θ 2 has a value of about 25<θ 2 <70 degrees.
18. The wireless communication device of claim 17 wherein the first Euler angle ϕ 1 of the support substrate layer is 0 degrees and the third Euler angle ψ 2 of the support substrate layer is 90 degrees.
19. The wireless communication device of claim 15 further including a functional layer between the piezoelectric layer and the support substrate layer.
20. The wireless communication device of claim 19 wherein the functional layer is a silicon dioxide layer having a thickness H2 with a value of about 0.3 L<H2<0.7 L, where L is a pitch between the fingers of the interdigital transducer electrode.