Piezoelectric actuators
Microelectromechanical systems with structures having piezoelectric actuators are described. The structures each have a body that supports piezoelectric islands. The piezoelectric islands have a first surface and a second opposite surface. The piezoelectric islands can be formed, in part, by forming cuts into a thick layer of piezoelectric material, attaching the cut piezoelectric layer to a body having etched features and grinding the piezoelectric layer to a thickness that is less than the depths of the cuts. Conductive material can be formed on the piezoelectric layer to form electrodes.
1. A device, comprising:
a handle layer; and
a piezoelectric layer having a first surface, a second surface, and a thickness that extends between the first surface and the second surface, wherein the first surface is bonded to the handle layer, the second surface has multiple cuts defining multiple actuator regions, and the multiple cuts extend through a portion of the thickness but not entirely through the thickness of the piezoelectric layer, and wherein the multiple cuts comprise at least one ground cut extending along a first direction and at least one isolation cut extending along a second direction perpendicular to the first direction.
2. The device of claim 1 , further comprising a bonding layer between the first surface and the handle layer.
3. The device of claim 2 , wherein the bonding layer comprises benzocyclobutene.
4. The device of claim 1 , wherein the handle layer comprises silicon.
5. The device of claim 1 , wherein the piezoelectric layer comprises a flatness of about 0.25 microns or less.
6. The device of claim 5 , wherein the flatness is about 0.1 microns or less.
7. The device of claim 1 , wherein the piezoelectric layer comprises a surface finish of about 5 nm Ra or less.
8. The device of claim 1 , wherein each of the multiple cuts has a cross-section that is rounded at a base of the each of the multiple cuts.
9. The device of claim 1 , further comprising a conductive layer on the second surface of the piezoelectric layer.
10. The device of claim 9 , wherein the conductive layer coats at least one wall of the ground cut but walls of the isolation cut are free of the conductive layer.
11. The device of claim 1 , further comprising alignment cuts that extend entirely through the thickness of the piezoelectric layer.
12. The device of claim 11 , wherein the alignment cuts extend into the handle layer.
13. The device of claim 11 , wherein the alignment cuts are formed in a region outside a portion of the piezoelectric layer where the multiple actuator regions are located.
14. The device of claim 11 , further comprising alignment slots formed in the handle layer that intersect the alignment cuts.
15. The device of claim 14 , wherein the alignment slots are orthogonal to the alignment cuts.
16. The device of claim 1 , wherein the handle layer is wider than the piezoelectric layer, and the device further comprises alignment cuts formed in the handle layer in a region outside the piezoelectric layer.
17. The device of claim 1 , wherein the thickness of the piezoelectric layer is less than about 200 microns.
18. The device of claim 17 , wherein the thickness of the piezoelectric layer is less than about 50 microns.
19. The device of claim 1 , wherein the handle layer has a thickness between about 400 to 1000 microns.
20. The device of claim 1 , wherein the piezoelectric layer has a density of about 7.5 g/cm 3 or more and a d31 coefficient of about 200 or more.
21. A device comprising:
a handle layer; and
a piezoelectric layer having a first surface, a second surface, and a thickness that extends between the first surface and the second surface, wherein the first surface is bonded to the handle layer, the second surface has multiple cuts defining multiple actuator regions, and the multiple cuts extend through a portion of the thickness but not entirely through the thickness of the piezoelectric layer, and wherein each of the multiple cuts cut has a cross-section that is rounded at a base of the each of the multiple cuts.
22. A device comprising:
a handle layer;
a piezoelectric layer having a first surface, a second surface, and a thickness that extends between the first surface and the second surface, wherein the first surface is bonded to the handle layer, the second surface has multiple cuts defining multiple actuator regions, the multiple cuts include at least one ground cut and at least one isolation cut, and each of the multiple cuts extends through a portion of the thickness but not entirely through the thickness of the piezoelectric layer; and
a conductive layer on the second surface of the piezoelectric layer, the conductive layer coating at least one wall of the ground cut but walls of the isolation cut are free of the conductive layer.