Method of fabricating rare-earth doped piezoelectric material with various amounts of dopants and a selected C-axis orientation
A method of fabricating a rare-earth element doped piezoelectric material having a first component, a second component and the rare-earth element. The method includes: providing a substrate; initially flowing hydrogen over the substrate; after the initially flowing of the hydrogen over the substrate, flowing the first component to form the rare-earth element doped piezoelectric material over a surface of a target, the target comprising the rare-earth metal in a certain atomic percentage; and sputtering the rare-earth element doped piezoelectric material from the target on the substrate.
1. A BAW resonator, comprising:
a first electrode disposed over a substrate;
an electropositive seed layer comprising aluminum and scandium (Al—Sc), and disposed over the substrate;
a piezoelectric layer disposed over the electropositive seed layer and comprising a rare-earth element doped piezoelectric material having a compression-negative (C N ) polarity, wherein the electropositive seed layer fosters growth of the piezoelectric layer having the compression-negative (C N ) polarity; and
a second electrode disposed over the rare-earth element doped piezoelectric material.
2. A BAW resonator as claimed in claim 1 , wherein the rare-earth element doped piezoelectric material comprises a first component and a second component.
3. A BAW resonator as claimed in claim 2 , wherein the rare-earth element is scandium (Sc), the first component is nitrogen (N), and the second component is aluminum (Al).
4. A bulk acoustic wave (BAW) resonator structure, comprising:
a first electrode disposed over a substrate;
a first non-ferroelectric piezoelectric layer disposed over the first electrode, the first non-ferroelectric piezoelectric layer having a first c-axis oriented along a first direction, and comprising a rare-earth element doped non-ferroelectric piezoelectric material;
a second electrode disposed over the first non-ferroelectric piezoelectric layer;
a second non-ferroelectric piezoelectric layer disposed over the first electrode, the second non-ferroelectric piezoelectric layer being adjacent to, and in direct contact with, the first non-ferroelectric piezoelectric layer, wherein the second non-ferroelectric piezoelectric layer has a second c-axis oriented in a second direction that is substantially antiparallel to the first direction; and
an acoustic reflector disposed in the substrate.
5. A BAW resonator structure as claimed in claim 4 , wherein the second non-ferroelectric piezoelectric layer comprises the rare-earth element doped non-ferroelectric piezoelectric material.
6. A BAW resonator structure as claimed in claim 5 , wherein the second non-ferroelectric piezoelectric layer has a piezoelectric coupling coefficient (e 33ip ) that is substantially equal in magnitude but opposite in sign to a piezoelectric coupling coefficient (e 33p ) of the first non-ferroelectric piezoelectric layer.
7. A BAW resonator structure as claimed in claim 5 , wherein the rare-earth element doped non-ferroelectric material comprises scandium doped aluminum nitride (AlScN).
8. A bulk acoustic wave (BAW) resonator structure, comprising:
a first electrode disposed over a substrate;
a cavity beneath the first electrode;
a first non-ferroelectric piezoelectric layer disposed over the first electrode, the first non-electric piezoelectric layer comprising a rare-earth element doped non-ferroelectric piezoelectric material, and having a first c-axis oriented along a first direction;
a second electrode disposed over the first non-ferroelectric piezoelectric layer, wherein an active region of the BAW resonator structure comprises an overlap of the first electrode and the second electrode with the cavity; and
a second non-ferroelectric piezoelectric layer disposed over the first electrode, the second non-ferroelectric piezoelectric layer being adjacent to, and in direct contact with, the first non-ferroelectric piezoelectric layer, the second non-ferroelectric piezoelectric layer having a second c-axis oriented in a second direction that is substantially antiparallel to the first direction, wherein the second electrode overlaps the second non-ferroelectric piezoelectric layer; and
an acoustic reflector disposed in the substrate.
9. A BAW resonator structure as claimed in claim 8 , wherein the first non-ferroelectric piezoelectric layer comprises the rare-earth element doped non-ferroelectric piezoelectric material, or the second non-ferroelectric piezoelectric layer comprises the rare-earth element doped non-ferroelectric piezoelectric material, or both.
10. A BAW resonator structure as claimed in claim 9 , wherein the second non-ferroelectric piezoelectric layer has a piezoelectric coupling coefficient (e 33ip ) that is substantially equal in magnitude but opposite in sign of a piezoelectric coupling coefficient (e 33p ) of the first non-ferroelectric piezoelectric layer.
11. A BAW resonator structure as claimed in claim 9 , wherein the rare-earth element doped non-ferroelectric piezoelectric material comprises scandium doped aluminum nitride (AlScN).
12. A BAW resonator as claimed in claim 1 , wherein the electropositive seed layer is comparatively pure.
13. A BAW resonator as claimed in claim 1 , wherein the electropositive seed layer is disposed directly on an upper surface of the first electrode.
14. A BAW resonator as claimed in claim 1 , wherein a thickness of the electropositive seed layer is in a range of approximately 50 {acute over (Å)} to approximately 1000 {acute over (Å)}.
15. A BAW resonator as claimed in claim 2 , wherein a thickness wherein a thickness of the electropositive seed layer is in a range of approximately 50 {acute over (Å)} to approximately 1000 {acute over (Å)}.
16. A BAW resonator as claimed in claim 7 , wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 0.5% to approximately 44%.
17. A BAW resonator as claimed in claim 7 , wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 2.5% to approximately 5%.
18. A BAW resonator as claimed in claim 7 , wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 0.5% to less than approximately 10.0%.
19. A BAW resonator as claimed in claim 11 , wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 0.5% to approximately 44%.
20. A BAW resonator as claimed in claim 11 , wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 2.5% to approximately 5%.
21. A BAW resonator as claimed in claim 11 , wherein atomic percentage of scandium in the scandium doped aluminum nitride (AlScN) is approximately 0.5% to less than approximately 10.0%.