MEMS process power
A transducer includes a first piezoelectric layer; and a second piezoelectric layer that is above the first piezoelectric layer; wherein the second piezoelectric layer is a more compressive layer with an average stress that is less than or more compressive than an average stress of the first piezoelectric layer.
1. A transducer comprising:
a first piezoelectric layer; and
a second piezoelectric layer that is above the first piezoelectric layer;
wherein the first piezoelectric layer has a non-uniform amount of residual stress that becomes more tensile as a thickness of the first piezoelectric layer increases, and the second piezoelectric layer has an average residual stress that is more compressive than an average residual stress of the first piezoelectric layer, or
wherein the first piezoelectric layer has a non-uniform amount of residual stress that becomes more compressive as the thickness of the first piezoelectric layer increases, and the second piezoelectric layer has an average residual stress that is more tensile than an average residual stress of the first piezoelectric layer.
2. The transducer of claim 1 , wherein being more compressive corresponds to a downward deflection in the second piezoelectric layer and wherein being more tensile corresponds to an upwards deflection in the second piezoelectric layer.
3. The transducer of claim 1 , wherein the second piezoelectric layer is a more compressive layer with an average residual stress that is less than or more compressive than the average residual stress of the first piezoelectric layer.
4. The transducer of claim 1 , wherein the second piezoelectric layer is a more tensile layer with an average residual stress that is greater than or less compressive than the average residual stress of the first piezoelectric layer.
5. The transducer of claim 1 , wherein a vertical stress of the second piezoelectric layer offsets a vertical stress of the first piezoelectric layer to reduce deflection in the transducer.
6. The transducer of claim 1 , wherein the transducer comprises a MEMS transducer, an acoustic transducer, a piezoelectric transducer or a microphone.
7. The transducer of claim 1 , further comprising a third intervening layer between the first and second piezoelectric layers.
8. The transducer of claim 7 , wherein the third intervening layer comprises a layer of molybdenum.
9. The transducer of claim 7 , wherein the average residual stress of the second piezoelectric layer compensates for a residual stress imparted by the third intervening layer.
10. The transducer of claim 1 , wherein the first and second piezoelectric layers form a cantilever.
11. The transducer of claim 1 , wherein the first and second piezoelectric layers comprise the same material.
12. The transducer of claim 1 , wherein the first piezoelectric layer comprises a different material than the second piezoelectric layer.
13. The transducer of claim 1 , wherein at least one of the first piezoelectric layer or the second piezoelectric layer comprises aluminum nitride.
14. The transducer of claim 1 , wherein the second piezoelectric layer is fabricated by adjusting a bias power to a level that produces the average residual stress that compensates for the non-uniform amount of residual stress through the thickness of the first piezoelectric layer.
15. The transducer of claim 14 , wherein the level of the bias power is used throughout an entirety of the fabrication of the second piezoelectric layer.
16. The transducer of claim 1 , wherein the second piezoelectric layer is fabricated by adjusting a gas flow rate to a level that produces the average residual stress that compensates for the non-uniform amount of residual stress through the thickness of the first piezoelectric layer.
17. The transducer of claim 1 , wherein the second piezoelectric layer comprises a non-uniform amount of vertical stress.
18. The transducer of claim 1 , wherein the first and second piezoelectric layers lie substantially flat.
19. The transducer of claim 18 , wherein the first and second piezoelectric layers lying substantially flat comprises the first and the second piezoelectric layers having less than a threshold amount of curvature or deflection.
20. The transducer of claim 1 , wherein the average residual stress of the second piezoelectric layer is more compressive than the average residual stress of the first piezoelectric layer.
21. The transducer of claim 1 , wherein the average residual stress of the second piezoelectric layer is more tensile than the average residual stress of the first piezoelectric layer.