Transverse bulk acoustic wave filter
A micro-transfer printable transverse bulk acoustic wave filter comprises a piezoelectric filter element having a top side, a bottom side, a left side, and a right side disposed over a sacrificial portion on a source substrate. A top electrode is in contact with the top side and a bottom electrode is in contact with the bottom side. A left acoustic mirror is in contact with the left side and a right acoustic mirror is in contact with the right side. The thickness of the transverse bulk acoustic wave filter is substantially less than its length or width and its length can be greater than its width. The transverse bulk acoustic wave filter can be disposed on, and electrically connected to, a semiconductor substrate comprising an electronic circuit to control the transverse bulk acoustic wave filter and form a composite heterogeneous device that can be micro-transfer printed.
1. A transverse bulk acoustic wave filter, comprising:
a piezoelectric filter element having a top side, a bottom side, a left side, and a right side, wherein the right side is opposed to the left side and the bottom side is opposed to the top side;
a top electrode in contact with the top side;
a bottom electrode in contact with the bottom side;
a left acoustic mirror in contact with the left side; and
a right acoustic mirror in contact with the right side,
wherein, when a voltage is applied across the top electrode and the bottom electrode, a resonant acoustic wave is formed in the piezoelectric filter element between the left and right acoustic mirrors.
2. The transverse bulk acoustic wave filter of claim 1 , wherein the piezoelectric filter element has a front side and a back side, and the transverse bulk acoustic wave filter comprises:
a front acoustic mirror in contact with the front side; and
a back acoustic mirror in contact with the back side.
3. The transverse bulk acoustic wave filter of claim 1 , comprising:
a bottom acoustic mirror in contact with the bottom electrode and, optionally, in contact with at least a portion of the bottom side.
4. The transverse bulk acoustic wave filter of claim 1 , comprising:
a top acoustic mirror in contact with the top electrode and, optionally, in contact with at least a portion of the top side.
5. The transverse bulk acoustic wave filter of claim 1 , wherein a distance between the top side and the bottom side is less than or equal to one half of a distance between the left side and the right side.
6. The transverse bulk acoustic wave filter of claim 1 , wherein the piezoelectric filter element has a front side and a back side, and wherein a distance between the top side and the bottom side is less than or equal to one half the distance between the front side and the back side.
7. The transverse bulk acoustic wave filter of claim 6 , wherein a distance between the front side and the back side is less than or equal to one half a distance between the left side and the right side.
8. The transverse bulk acoustic wave filter of claim 1 , wherein a cross section of the piezoelectric filter element is substantially rectangular.
9. The transverse bulk acoustic wave filter of claim 1 , wherein the piezoelectric filter element has a front side and a back side, the transverse bulk acoustic wave filter comprises a front acoustic mirror in contact with the front side and a back acoustic mirror in contact with the back side, and wherein the applied voltage forms a resonant acoustic wave in the piezoelectric filter element between the front and back acoustic mirrors.
10. The transverse bulk acoustic wave filter of claim 1 , wherein the piezoelectric filter element has a top acoustic mirror in contact with the top electrode and a bottom acoustic mirror in contact with the bottom electrode and wherein the applied voltage forms a resonant acoustic wave in the piezoelectric filter element between the top and bottom acoustic mirrors.
11. The transverse bulk acoustic wave filter of claim 1 , comprising a top electrical conductor in electrical contact with the top electrode and a bottom electrical conductor in contact with the bottom electrode, and
wherein the top electrical conductor is disposed at least partially on, in, or as part of the left acoustic mirror and the bottom electrical conductor is disposed at least partially on, in, or as part of the right acoustic mirror, or
wherein the top electrical conductor is insulated from the left side by a dielectric structure that forms at least a portion of the left acoustic mirror and the bottom electrical conductor is insulated from the right acoustic mirror by a dielectric structure that forms at least a portion of the right acoustic mirror.
12. A transverse acoustic wave filter wafer, comprising:
a source wafer comprising substrate material;
a patterned sacrificial layer forming sacrificial portions on, over, or in the substrate material, a surface of the substrate material, the source wafer, or a surface of the source wafer, the sacrificial portions defining separate anchors between the sacrificial portions; and
a transverse bulk acoustic wave filter disposed entirely over each sacrificial portion, wherein the transverse bulk acoustic wave filter comprises
a piezoelectric filter element having a top side, a bottom side, a left side, and a right side, wherein the right side is opposed to the left side and the bottom side is opposed to the top side;
a top electrode in contact with the top side; a bottom electrode in contact with the bottom side;
a left acoustic mirror in contact with the left side; and
a right acoustic mirror in contact with the right side.
13. A transverse bulk acoustic wave filter, comprising:
a piezoelectric filter element having a top side, a bottom side, a left side, and a right side, wherein the right side is opposed to the left side and the bottom side is opposed to the top side;
a top electrode in contact with the top side;
a bottom electrode in contact with the bottom side;
a left acoustic mirror in contact with the left side;
a right acoustic mirror in contact with the right side; and
a fractured or separated tether.
14. A transverse bulk acoustic wave filter, comprising:
a piezoelectric filter element having a top side, a bottom side, a left side, and a right side, wherein the right side is opposed to the left side and the bottom side is opposed to the top side;
a top electrode in contact with the top side;
a bottom electrode in contact with the bottom side;
a left acoustic mirror in contact with the left side;
a right acoustic mirror in contact with the right side; and
a support substrate comprising top and bottom circuit connection pads and wherein the bottom electrode is adhered to the support substrate, the top circuit connection pad is electrically connected to the top electrode, and the bottom circuit connection pad is electrically connected to the bottom electrode.
15. The transverse bulk acoustic wave filter of claim 14 , wherein the support substrate is a semiconductor substrate and the transverse bulk acoustic wave filter further comprises an active electronic circuit formed in or on the semiconductor substrate, the active electronic circuit electrically connected to the top and bottom circuit connection pads.
16. The transverse bulk acoustic wave filter of claim 15 , wherein the active electronic circuit is disposed at least partially between the piezoelectric filter element and the support substrate.
17. The transverse bulk acoustic wave filter of claim 15 , wherein the piezoelectric filter element is a first piezoelectric filter element and the transverse bulk acoustic wave filter comprises:
a second piezoelectric filter element, wherein the second piezoelectric filter element has a top side and a bottom side opposed to the top side and a left side and a right side opposed to the left side,
a top electrode in contact with the top side,
a bottom electrode in contact with the bottom side,
a left acoustic mirror in contact with the left side, and
a right acoustic mirror in contact with the right side; and
wherein the top and bottom electrodes of the second piezoelectric filter element are electrically connected to the active electronic circuit.
18. A transverse acoustic wave filter wafer, comprising:
a device wafer comprising substrate material;
a patterned sacrificial layer forming sacrificial portions on, over, or in the substrate material, a surface of the substrate material, the device wafer, or a surface of the device wafer, the sacrificial portions defining separate anchors between the sacrificial portions;
a transverse bulk acoustic wave filter disposed entirely over each sacrificial portion, the transverse bulk acoustic wave filter comprising a piezoelectric filter element having a top side, a bottom side, a left side, and a right side, wherein the right side is opposed to the left side and the bottom side is opposed to the top side, a top electrode in contact with the top side, a bottom electrode in contact with the bottom side, a left acoustic mirror in contact with the left side, a right acoustic mirror in contact with the right side, and a fractured or separated tether; and
an electrical connection electrically connected to the top electrode and an electrical connection electrically connected to the bottom electrode.
19. The acoustic wave filter wafer of claim 18 , comprising a semiconductor layer disposed entirely over each sacrificial portion between the sacrificial portion and the transverse bulk acoustic wave filter, the semiconductor layer comprising an active electronic circuit to which the electrical connections are electrically connected.
20. A transverse bulk acoustic wave filter, comprising:
a piezoelectric filter element having a top side, a bottom side, a left side, and a right side, wherein the right side is opposed to the left side and the bottom side is opposed to the top side;
a top electrode in contact with the top side;
a bottom electrode in contact with the bottom side;
a left acoustic mirror in contact with the left side; and
a right acoustic mirror in contact with the right side,
wherein at least one of the left acoustic mirror and right acoustic mirror comprises a plurality of alternating high-impedance and low-impedance sub-layers.