Bulk acoustic wave (BAW) resonator structure having an electrode with a cantilevered portion and a piezoelectric layer with multiple dopants
A bulk acoustic wave (BAW) resonator, comprises: a first electrode; a second electrode comprising a plurality of sides. At least one of the sides comprises a cantilevered portion. The bulk acoustic wave (BAW) resonator also comprises a piezoelectric layer disposed between the first and second electrodes. The piezoelectric layer comprises a piezoelectric material doped with a plurality of rare earth elements, and the cantilevered portion extends above the piezoelectric layer. The bulk acoustic wave (BAW) resonator comprises a gap between the cantilevered portion and the piezoelectric layer.
1. An acoustic resonator, comprising:
a first electrode;
a second electrode comprising a plurality of sides, wherein at least one of the sides comprises a cantilevered portion;
a piezoelectric layer disposed between the first and second electrodes, the piezoelectric layer comprising a piezoelectric material doped with a plurality of rare earth elements, wherein the cantilevered portion extends above the piezoelectric layer; and
a gap between the cantilevered portion and the piezoelectric layer.
2. An acoustic resonator as claimed in claim 1 , further comprising a reflective element disposed beneath the first electrode, the second electrode and the piezoelectric layer, wherein a contacting overlap of the reflective element, the first electrode, the second electrode and the piezoelectric layer defines an active area of the acoustic resonator.
3. An acoustic resonator as claimed in claim 2 , wherein the cantilevered portion of the second electrode extends beyond a termination of the active area.
4. An acoustic resonator as claimed in claim 2 , further comprising a bridge adjacent to a termination of the active area of the acoustic resonator.
5. An acoustic resonator as claimed in claim 4 , wherein the gap is a first gap, and the bridge comprises a second gap, which exists in a region between the second electrode and the piezoelectric layer.
6. An acoustic resonator as claimed in claim 2 , further comprising a frame element.
7. An acoustic resonator as claimed in claim 6 , wherein the frame element is a recessed frame element.
8. An acoustic resonator as claimed in claim 6 , wherein the frame element comprises a raised frame element.
9. An acoustic resonator as claimed in claim 1 , wherein all but one of the plurality of sides of the second electrode comprises the cantilevered portion.
10. An acoustic resonator as claimed in claim 9 , further comprising an electrical connection to the one of the plurality of sides of the second electrode that does not comprise a cantilevered portion.
11. An acoustic resonator as claimed in claim 1 , wherein the piezoelectric material comprises aluminum nitride (AlN).
12. An acoustic resonator as claimed in claim 11 , wherein the plurality of rare earth elements comprises two rare earth elements incorporated into a crystal lattice of the AlN piezoelectric material.
13. An acoustic resonator as claimed in claim 12 , wherein the plurality of rare earth elements comprises scandium (Sc) and erbium (Er).
14. An acoustic resonator as claimed in claim 13 , wherein the plurality of rare earth elements further comprises yttrium (Y).
15. An acoustic resonator as claimed in claim 13 , wherein a concentration of each of the scandium and the erbium is less than approximately 10 atomic percent of the piezoelectric material.
16. An acoustic resonator as claimed in claim 15 , wherein the concentration of each of the scandium and the erbium is less than approximately one atomic percent of the piezoelectric material.
17. An acoustic resonator as claimed in claim 16 , wherein the concentration of scandium is approximately 0.63 atomic percent of the piezoelectric material, and the concentration of erbium is approximately 0.34 atomic percent of the piezoelectric material.
18. An acoustic resonator as claimed in claim 11 , wherein the plurality of rare earth elements comprises more than two rare earth elements incorporated into a crystal lattice of the AlN piezoelectric material.
19. An acoustic resonator as claimed in claim 11 , wherein the piezoelectric layer is provided using a target formed of an alloy comprising aluminum and the plurality of doping elements, and sputtering the aluminum alloy from the target over the bottom electrode using a plasma comprising nitrogen.
20. An acoustic resonator as claimed in claim 1 , wherein the piezoelectric layer is provided using a plurality of targets formed of aluminum and the plurality of doping elements, respectively, and sputtering the aluminum and the plurality of doping elements from the corresponding targets over the bottom electrode using a plasma comprising nitrogen.
21. A microelectromechanical system (MEMS) device comprising the acoustic resonator of claim 1 .
22. An acoustic resonator, comprising:
a first electrode;
a second electrode comprising a plurality of sides, wherein at least one of the sides comprises a cantilevered portion;
a piezoelectric layer disposed between the first and second electrodes, the piezoelectric layer comprising a piezoelectric material doped with a plurality of rare earth elements, wherein the cantilevered portion extends above the piezoelectric layer;
a reflective element disposed beneath the first electrode, the second electrode and the piezoelectric layer, a contacting overlap of the reflective element, the first electrode, the second electrode and the piezoelectric layer defining an active area of the acoustic resonator, wherein the first electrode substantially covers the reflective element, and the piezoelectric layer extends over an edge of the first electrode; and
a bridge disposed adjacent to a termination of the active area of the acoustic resonator, the bridge extending past an edge of the reflective element.
23. An acoustic resonator as claimed in claim 22 , wherein the cantilevered portion of the second electrode extends beyond a termination of the active area.
24. An acoustic resonator as claimed in claim 22 , further comprising a frame element.
25. An acoustic resonator as claimed in claim 24 , wherein the frame element is a recessed frame element.
26. An acoustic resonator as claimed in claim 24 , wherein the frame element comprises a raised frame element.
27. An acoustic resonator as claimed in claim 22 , wherein the bridge comprises a gap, and the gap exists in a region between the second electrode and the piezoelectric layer.
28. An acoustic resonator as claimed in claim 22 , wherein all but one of the plurality of sides of the second electrode comprise the cantilevered portion.
29. An acoustic resonator as claimed in claim 22 , wherein the piezoelectric material comprises aluminum nitride (AlN).
30. An acoustic resonator as claimed in claim 29 , wherein the plurality of rare earth elements comprises two rare earth elements incorporated into a crystal lattice of the AlN piezoelectric material.
31. An acoustic resonator as claimed in claim 22 , wherein the plurality of rare earth elements comprises more than two rare earth elements incorporated into a crystal lattice of the AlN piezoelectric material.
32. An acoustic resonator as claimed in claim 22 , wherein the plurality of rare earth elements comprises scandium (Sc) and erbium (Er).
33. An acoustic resonator as claimed in claim 32 , wherein the plurality of rare earth elements further comprises yttrium (Y).
34. An acoustic resonator as claimed in claim 32 , wherein a concentration of each of the scandium and the erbium is less than approximately 10 atomic percent of the piezoelectric material.
35. An acoustic resonator as claimed in claim 34 , wherein the concentration of each of the scandium and the erbium is less than approximately one atomic percent of the piezoelectric material.
36. An acoustic resonator as claimed in claim 35 , wherein the concentration of scandium is approximately 0.63 atomic percent of the piezoelectric material, and the concentration of erbium is approximately 0.34 atomic percent of the piezoelectric material.
37. An acoustic resonator as claimed in claim 22 , wherein the piezoelectric layer is provided using a target formed of an alloy comprising aluminum and the plurality of doping elements, and sputtering the aluminum alloy from the target over the bottom electrode using a plasma comprising nitrogen.
38. An acoustic resonator as claimed in claim 22 , wherein the piezoelectric layer is provided using a plurality of targets formed of aluminum and the plurality of doping elements, respectively, and sputtering the aluminum and the plurality of doping elements from the corresponding targets over the bottom electrode using a plasma comprising nitrogen.
39. A microelectromechanical system (MEMS) device comprising the acoustic resonator of claim 22 .