Surface acoustic wave devices using beryllium conductors
View Patent ↗Acoustic wave devices and methods of fabricating acoustic wave devices. A device includes a piezoelectric substrate and a conductor pattern formed on a surface of the piezoelectric substrate. The conductor pattern includes an interdigitated transducer (IDT) of a surface acoustic wave (SAW) resonator. The conductor pattern includes a substantially beryllium layer proximate the surface of the piezoelectric substrate.
1. A device comprising:
a rotated Y-cut LiTaO3 piezoelectric substrate having a cut angle in a range of 35° to 45°; and
a conductor pattern formed on a surface of the piezoelectric substrate, the conductor pattern including an interdigital transducer (IDT) of a surface acoustic wave (SAW) resonator, the SAW resonator oriented for an X propagation direction,
wherein the conductor pattern includes a substantially beryllium layer formed proximate the surface of the piezoelectric substrate, and
the cut angle and a thickness of the conductor pattern are collectively configured to maximize a Q-factor of the SAW resonator at a frequency near a resonant frequency of the SAW resonator.
2. The device of claim 1 , wherein the substantially beryllium layer has a thickness defined by 0.05≤h/2p≤0.20, where h is the substantially beryllium layer film thickness and p is a geometric period of the IDT.
3. The device of claim 1 , wherein the conductor pattern includes one or more intervening layers between the substantially beryllium layer and the surface of the piezoelectric substrate.
4. The device of claim 3 , wherein the one or more intervening layers include an adhesion layer.
5. The device of claim 1 , wherein the conductor pattern includes a conduction enhancement layer over the substantially beryllium layer.
6. The device of claim 5 , wherein the conduction enhancement layer is gold.
7. The device of claim 1 , wherein at least a portion of the conductor pattern is formed in grooves in the piezoelectric substrate.
8. A method of fabricating an acoustic wave device comprising:
forming a conductor pattern on a surface of a piezoelectric substrate, the conductor pattern including an interdigital transducer (IDT) of a surface acoustic wave (SAW) resonator, the SAW resonator is oriented for an X propagation direction
wherein the conductor pattern includes a substantially beryllium layer proximate the surface of the piezoelectric substrate,
the piezoelectric substrate is rotated Y-cut LiTaO3 with a cut angle in a range of 35° to 45°; and
the cut angle and a thickness of the conductor pattern are collectively configured to maximize a Q-factor of the SAW resonator at a frequency near a resonant frequency of the SAW resonator.
9. The method of claim 8 , wherein the substantially beryllium layer has a thickness defined by 0.05≤h/2p≤0.20, where h is the substantially beryllium layer film thickness and p is the geometric period of the IDT.
10. The method of claim 8 , wherein the conductor pattern includes the substantially beryllium layer and one or more layers of other materials between the substantially beryllium layer and the surface of the piezoelectric substrate.
11. The method of claim 10 , wherein the one or more layers include an adhesion layer.
12. The method of claim 8 , wherein the conductor pattern includes the substantially beryllium layer and a conduction enhancement layer over the substantially beryllium layer.
13. The method of claim 12 , wherein the conduction enhancement layer is gold.
14. The method of claim 8 , further comprising:
prior to forming the conductor pattern, forming grooves in the surface of the substrate, wherein at least a portion of the conductor pattern is formed in the grooves.
15. A device comprising:
a rotated Y-cut LiTaO3 piezoelectric substrate having a cut angle in a range of 45° to 50°; and
a conductor pattern formed on a surface of the piezoelectric substrate, the conductor pattern including an interdigital transducer (IDT) of a surface acoustic wave (SAW) resonator, the SAW resonator oriented for an X propagation direction,
wherein the conductor pattern includes a substantially beryllium layer formed proximate the surface of the piezoelectric substrate, and
the cut angle and a thickness of the conductor pattern are collectively configured to maximize a Q-factor of the SAW resonator at a frequency near an anti-resonant frequency of the SAW resonator.
16. The device of claim 15 , wherein the substantially beryllium layer has a thickness defined by 0.05≤h/2p≤0.20, where h is the substantially beryllium layer film thickness and p is a geometric period of the IDT.
17. The device of claim 15 , wherein the conductor pattern includes one or more intervening layers between the substantially beryllium layer and the surface of the piezoelectric substrate.
18. The device of claim 17 , wherein the one or more intervening layers include an adhesion layer.
19. The device of claim 15 , wherein the conductor pattern includes a conduction enhancement layer over the substantially beryllium layer.
20. The device of claim 19 , wherein the conduction enhancement layer is gold.
21. The device of claim 15 , wherein at least a portion of the conductor pattern is formed in grooves in the piezoelectric substrate.
22. A method of fabricating an acoustic wave device comprising:
forming a conductor pattern on a surface of a piezoelectric substrate, the conductor pattern including an interdigital transducer (IDT) of a surface acoustic wave (SAW) resonator, the SAW resonator is oriented for an X propagation direction
wherein the conductor pattern includes a substantially beryllium layer proximate the surface of the piezoelectric substrate,
the piezoelectric substrate is rotated Y-cut LiTaO3 with a cut angle in a range of 45° to 50°, and
the cut angle and a thickness of the conductor pattern are collectively configured to maximize a Q-factor of the SAW resonator at a frequency near an anti-resonant frequency of the SAW resonator.
23. The method of claim 22 , wherein the substantially beryllium layer has a thickness defined by 0.05≤h/2p≤0.20, where h is the substantially beryllium layer film thickness and p is the geometric period of the IDT.
24. The method of claim 22 , wherein the conductor pattern includes the substantially beryllium layer and one or more layers of other materials between the substantially beryllium layer and the surface of the piezoelectric substrate.
25. The method of claim 24 , wherein the one or more layers include an adhesion layer.
26. The method of claim 22 , wherein the conductor pattern includes the substantially beryllium layer and a conduction enhancement layer over the substantially beryllium layer.
27. The method of claim 26 , wherein the conduction enhancement layer is gold.
28. The method of claim 22 , further comprising:
prior to forming the conductor pattern, forming grooves in the surface of the substrate,
wherein at least a portion of the conductor pattern is formed in the grooves.