Recessed frames in thickness mode piezoelectric resonators
In some examples, an apparatus includes a first metal layer having a thickness, a piezoelectric material layer having a first side and a second side that is opposite the first side, the piezoelectric material layer first side abutting the first metal layer, the piezoelectric material layer second side having recesses, and a second metal layer abutting the piezoelectric material layer second side, the second metal layer having extensions that fill the recesses to form a metal frame that is at least partially recessed into the piezoelectric material layer. The first metal layer, the piezoelectric material layer, and the second metal layer form a resonator body. The metal frame has a shape governing a resonant mode of the resonator body.
1 . An apparatus, comprising:
a first metal layer;
a second metal layer; and
a piezoelectric material layer between the first and second metal layer along an axis, the piezoelectric material layer including first portions and second portions, each of the second portions having a smaller thickness than the first portions and overlapping both the first and second metal layers.
2 . The apparatus of claim 1 , wherein the axis is a first axis, parts of the first or second metal layers abutting the first and second portions are part of a metal frame, and the metal frame is configurable to set a resonance quality factor and set spurious resonant modes along a second axis angled from the first axis.
3 . The apparatus of claim 1 , wherein the axis is a first axis, the first and second portions are part of recesses each having a first width along a second axis angled from the first axis, adjacent recesses are separated by a second width.
4 . The apparatus of claim 3 , wherein a ratio of the first width to the second width is within a range of 3:1.
5 . The apparatus of claim 3 , wherein the first and second metal layers and the piezoelectric material layer form a resonator having an operating wavelength, and an edge of one of the first or second metal layers is separated from one of the second portions by a distance that is an odd multiple of a quarter of the operating wavelength.
6 . The apparatus of claim 1 , further comprising an acoustic reflector opposing the first metal layer.
7 . The apparatus of claim 6 , wherein the acoustic reflector is configurable to confine energy around a parallel resonance frequency of a resonator comprising the first and second metal layers and the piezoelectric material layer.
8 . The apparatus of claim 6 , wherein the acoustic reflector is a first acoustic reflector, further comprising a second acoustic reflector opposing the second metal layer.
9 . The apparatus of claim 8 , wherein the first acoustic reflector and the second acoustic reflector are configured to confine energy around a parallel resonance frequency of a resonator comprising the first and second metal layers and the piezoelectric material layer.
10 . A system, comprising:
a piezoelectric resonator including:
a first metal layer;
a second metal layer; and
a piezoelectric material layer between the first and second metal layer along an axis, the piezoelectric material layer including first portions and second portions, each of the second portions having a smaller thickness than the first portions and overlapping both the first and second metal layers; and
a controller coupled to the first metal layer and the second metal layer, the controller configurable to drive the piezoelectric material layer into resonance.
11 . The system of claim 10 , wherein the axis is a first axis, the first and second portions are part of recesses each having a first width along a second axis angled from the first axis, adjacent recesses are separated by a second width.
12 . The system of claim 11 , wherein a ratio of the first width to the second width is within a range of 3:1.
13 . The system of claim 11 , wherein the first and second metal layers and the piezoelectric material layer are part of a resonator having an operating wavelength, and an edge of one of the first or second metal layers is separated from one of the second portions by a distance that is an odd multiple of a quarter of the operating wavelength.
14 . The system of claim 11 , further comprising an acoustic reflector opposing the first metal layer.
15 . The system of claim 14 , wherein the acoustic reflector is configurable to confine energy around a parallel resonance frequency of a resonator comprising the first and second metal layers and the piezoelectric material layer.
16 . A device, comprising:
a first metal layer;
a second metal layer; and
a piezoelectric material layer between the first metal layer and the second metal layer, the piezoelectric material layer having recesses that overlap with the first and second metal layer.
17 . The device of claim 16 , wherein the piezoelectric material layer is between the first and second metal layers along a first axis, parts of the first or second metal layers abutting the recesses are part of a metal frame, and the metal frame is configurable to set a resonance quality factor and set spurious resonant modes along a second axis angled from the first axis.
18 . The device of claim 16 , further comprising a controller coupled to the first and second metal layers and configurable to drive the piezoelectric material layer into resonance.
19 . The device of claim 16 , wherein each of the recesses has a first width, the recesses being separated from each other by at least a second width.
20 . The device of claim 19 , wherein a ratio of the first width to the second width is within a range of 3:1.
21 . The apparatus of claim 1 , further comprising:
a substrate; and
support portions on the substrate,
wherein the second metal layer is coupled to the support portions.
22 . The apparatus of claim 1 , further comprising a substrate having a surface, wherein the second metal layer is over and conformal to the surface of the substrate.
23 . The apparatus of claim 1 , wherein the first and second metal layers and the piezoelectric material layer is part of an oscillator circuit having an output, and the apparatus further comprises a system coupled to the oscillator circuit.
24 . The apparatus of claim 1 , wherein the first and second metal layers and the piezoelectric material layer is part of an acoustic sensing circuit.
25 . The apparatus of claim 1 , further comprising an oscillator including the first metal layer, the second metal layer, and the piezoelectric material layer.
26 . The apparatus of claim 25 , wherein the oscillator is a frequency reference oscillator, and the apparatus further comprises a device coupled to the frequency reference oscillator.
27 . The apparatus of claim 1 , further comprising an ultrasonic diagnostic device including the first metal layer, the second metal layer, and the piezoelectric material layer.