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 attached to the substrate. A second portion of the piezoelectric forms a diaphragm suspended over a cavity in the substrate. An interdigital transducer (IDT) is formed on a surface of the piezoelectric plate, the IDT including first and second busbars disposed on the first portion and interleaved IDT fingers disposed 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, an overlapping distance of the interleaved IDT fingers defining an aperture of the acoustic resonator device; and
a plurality of spaces in the diaphragm between the aperture and the first busbar and the aperture and the second busbar, wherein a tether provides an electrical connection between at least 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
the tether 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 the tether forms an oblique angle with a long direction of the at least one 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 the tether is curved.
9. The acoustic resonator device of claim 1 , wherein
the tether is continuously curved.
10. The acoustic resonator device of claim 1 , the tether comprising:
a first segment extending from the first or second busbar;
a third segment extending from the diaphragm colinear with the at least one 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 at least one IDT finger.
11. The acoustic resonator device of claim 1 , wherein
a width of the tether is greater than a width of the at least one IDT finger.
12. The acoustic resonator device of claim 11 , wherein
the width of the tether 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, an overlapping distance of the interleaved IDT fingers defining an aperture of the acoustic resonator device; and
a plurality of spaces in the diaphragm between the aperture and the first busbar and the aperture and the second busbar, a tether electrically connecting at least one of the interleaved IDT fingers and 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
the tether 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 the tether forms an oblique angle with a long direction of the at least one 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 , the tether comprising:
a first segment extending from the first or second busbar;
a third segment extending from the diaphragm colinear with the at least one 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 at least one interleaved IDT finger.
21. The acoustic resonator device of claim 13 , wherein
at least a portion of the tether is curved.
22. The acoustic resonator device of claim 13 , wherein
the tether is continuously curved.
23. The acoustic resonator device of claim 13 , wherein
a width of the tether is greater than a width of the at least one interleaved IDT finger.
24. The acoustic resonator device of claim 23 , wherein
the width of the tether is one-half of a pitch of the interleaved IDT fingers.