Transversely-excited film bulk acoustic resonator with tether-supported diaphragm
An acoustic resonator device includes a substrate and a piezoelectric plate. A first portion of the piezoelectric plate is on the substrate. A second portion of the piezoelectric forms a diaphragm suspended over a cavity in the substrate. An interdigital transducer (IDT) is on a surface of the piezoelectric plate, the IDT including first and second busbars on the first portion and interleaved IDT fingers on the diaphragm. A plurality of tethers support the diaphragm over the cavity, each tether providing an electrical connection between a corresponding one of the interleaved IDT fingers and one of the first and second busbars.
1. An acoustic resonator device comprising:
a substrate;
a piezoelectric plate, a first portion of the piezoelectric plate on the substrate, and a second portion of the piezoelectric plate forming a diaphragm suspended over a cavity in the substrate;
an interdigital transducer (IDT) on a surface of the piezoelectric plate, the IDT comprising first and second busbars on the first portion and interleaved IDT fingers on the diaphragm; and
a plurality of tethers supporting the diaphragm over the cavity, each tether providing an electrical connection between a corresponding one of the interleaved IDT fingers and one of the first and second busbars.
2. The acoustic resonator device of claim 1 , wherein
the first and second busbars are on opposite sides of the cavity.
3. The acoustic resonator device of claim 2 , wherein
the interleaved IDT fingers are connected to the first and second busbars alternately.
4. The acoustic resonator device of claim 1 , wherein
the interleaved IDT fingers comprise a first conductor level, and
each tether of the plurality of tethers comprises the first conductor level and a corresponding section of the piezoelectric plate connecting the first portion and the diaphragm.
5. The acoustic resonator device of claim 4 , wherein
each of the first and second busbars comprises the first conductor level and a second conductor level.
6. The acoustic resonator device of claim 1 , wherein
a portion of each tether of the plurality of tethers forms an oblique angle with a long direction of the corresponding interleaved IDT finger.
7. The acoustic resonator device of claim 6 , wherein
the oblique angle is greater than or equal to 30 degrees and less than or equal to 60 degrees.
8. The acoustic resonator device of claim 1 , wherein
at least a portion of each tether of the plurality of tethers is curved.
9. The acoustic resonator device of claim 1 , wherein
each tether of the plurality of tethers is continuously curved.
10. The acoustic resonator device of claim 1 , each tether of the plurality of tethers comprising:
a first segment extending from the first or second busbar;
a third segment extending from the diaphragm colinear with the corresponding IDT finger; and
a second segment joining the first segment and the third segment, the second segment forming an oblique angle with a long direction of the corresponding IDT finger.
11. The acoustic resonator device of claim 1 , wherein
a width of each tether of the plurality of tethers is greater than a width of the corresponding IDT finger.
12. The acoustic resonator device of claim 11 , wherein
the width of each tether of the plurality of tethers is one-half of a pitch of the IDT fingers.
13. An acoustic resonator device comprising:
a piezoelectric plate on a substrate, a portion of the piezoelectric plate forming a diaphragm suspended over a cavity in the substrate;
an interdigital transducer (IDT) on the piezoelectric plate, the IDT comprising interleaved IDT fingers on the diaphragm and first and second busbars not on the diaphragm; and
a plurality of tethers supporting the diaphragm over the cavity, each tether electrically connecting a corresponding one of the interleaved IDT fingers and one of the first and second busbars by spanning an open space between the diaphragm and the one of the first and second busbars.
14. The acoustic resonator device of claim 13 , wherein
the first and second busbars are on opposite sides of the cavity.
15. The acoustic resonator device of claim 14 , wherein
the interleaved IDT fingers are connected to the first or second busbars alternately.
16. The acoustic resonator device of claim 13 , wherein
the interleaved IDT fingers comprise a first conductor level, and
each tether of the plurality of tethers comprises the first conductor level and a corresponding portion of the piezoelectric plate.
17. The acoustic resonator device of claim 16 , wherein
each of the first and second busbars comprises the first conductor level and a second conductor level.
18. The acoustic resonator device of claim 13 , wherein
a section of each tether of the plurality of tethers forms an oblique angle with a long direction of the corresponding interleaved IDT finger.
19. The acoustic resonator device of claim 18 , wherein
the oblique angle is greater than or equal to 30 degrees and less than or equal to 60 degrees.
20. The acoustic resonator device of claim 18 , each tether of the plurality of tethers comprising:
a first segment extending from the first or second busbar;
a third segment extending from the diaphragm colinear with the corresponding IDT finger; and
a second segment joining the first segment and the third segment, the second segment forming the oblique angle with the long direction of the corresponding interleaved IDT finger.
21. The acoustic resonator device of claim 13 , wherein
at least a portion of each tether of the plurality of tethers is curved.
22. The acoustic resonator device of claim 13 , wherein
each tether of the plurality of tethers is continuously curved.
23. The acoustic resonator device of claim 13 , wherein
a width of each tether of the plurality of tethers is greater than a width of the corresponding interleaved IDT finger.
24. The acoustic resonator device of claim 23 , wherein
the width of each tether of the plurality of tethers is one-half of a pitch of the interleaved IDT fingers.