Transversely-excited film bulk acoustic resonator with optimized electrode thickness, mark, and pitch
Acoustic resonators and filter devices. An acoustic resonator includes a piezoelectric plate having front and back surfaces, a portion of the piezoelectric plate forming a diaphragm, and a conductor pattern on the front surface, the conductor pattern including an interdigital transducer (IDT), fingers of the IDT on the diaphragm. A thickness of the interleaved fingers is greater than or equal to 0.85 times a thickness of the piezoelectric plate and less than or equal to 2.5 times the thickness of the piezoelectric plate. The IDT comprises a first portion having a first pitch and a first mark and a second portion having a second pitch and a second mark not equal to the first pitch and first mark.
1. An acoustic resonator, comprising:
a piezoelectric plate having front and back surfaces, a portion of the piezoelectric plate forming a diaphragm; and
a conductor pattern on the front surface, the conductor pattern comprising an interdigital transducer (IDT), fingers of the IDT on the diaphragm,
wherein a thickness of the interleaved fingers is greater than or equal to 0.85 times a thickness of the piezoelectric plate and less than or equal to 2.5 times the thickness of the piezoelectric plate, and
wherein the IDT comprises a first portion having a first pitch and a first mark and a second portion having a second pitch and a second mark not equal to the first pitch and first mark.
2. The acoustic resonator of claim 1 , wherein the piezoelectric plate is lithium niobite or lithium tantalate.
3. The acoustic resonator of claim 2 , wherein the piezoelectric plate is one of Z-cut, rotated Z-cut, and rotated Y-cut.
4. The acoustic resonator of claim 1 , wherein the IDT is one or more of aluminum, an aluminum alloy, copper, a copper alloy, beryllium, gold, tungsten, and molybdenum.
5. The acoustic resonator of claim 1 , wherein a radio frequency signal applied to the IDT excites a primary acoustic mode within the piezoelectric plate.
6. The acoustic resonator of claim 5 , wherein the primary acoustic mode is a shear acoustic mode.
7. The acoustic resonator of claim 1 further comprising the substrate, wherein the back surface is attached to a surface of the substrate, and wherein the diaphragm spans a cavity in the substrate.
8. The acoustic resonator of claim 7 , wherein the substrate is one or more of silicon, sapphire, and quartz.
9. The acoustic resonator of claim 7 , wherein the cavity is a recess in the substrate.
10. The acoustic resonator of claim 7 , wherein the cavity extends through a thickness of the substrate.
11. A filter device, comprising:
a piezoelectric plate having front and back surfaces, portions of the piezoelectric plate forming one or more diaphragms; and
a conductor pattern on the front surface, the conductor pattern comprising a plurality of interdigital transducers (IDTs), interleaved fingers of the IDTs on the one or more diaphragms,
wherein a thickness of the interleaved fingers is greater than or equal to 0.85 times a thickness of the piezoelectric plate and less than or equal to 2.5 times the thickness of the piezoelectric plate, and
wherein at least one of the plurality of IDTs comprises a first portion having a first pitch and a first mark and a second portion having a second pitch and a second mark not equal to the first pitch and first mark.
12. The filter device of claim 11 , wherein the piezoelectric plate is lithium niobite or lithium tantalate.
13. The filter device of claim 12 , wherein the piezoelectric plate is one of Z-cut, rotated Z-cut, and rotated Y-cut.
14. The filter device of claim 11 , wherein each of the plurality of IDTs is one or more of aluminum, an aluminum alloy, copper, a copper alloy, beryllium, gold, tungsten, and molybdenum.
15. The filter device of claim 11 , wherein a radio frequency signal applied to each of the plurality of IDTs excites a respective primary acoustic mode within the piezoelectric plate.
16. The filter device of claim 14 , wherein the respective primary acoustic mode is a shear acoustic mode.
17. The filter device of claim 11 further comprising a substrate, wherein the back surface is attached to a surface of the substrate, and wherein the one or more diaphragms spans a respective cavity in the substrate.
18. The filter device of claim 17 , wherein the substrate is one or more of silicon, sapphire, and quartz.
19. The filter device of claim 17 , wherein the respective cavities are recesses in the substrate.
20. The filter device of claim 17 , wherein the respective cavities extend through a thickness of the substrate.