Plate wave devices with wave confinement structures and fabrication methods
A micro-electrical-mechanical system (MEMS) guided wave device includes a single crystal piezoelectric layer and at least one guided wave confinement structure configured to confine a laterally excited wave in the single crystal piezoelectric layer. A bonded interface is provided between the single crystal piezoelectric layer and at least one underlying layer. A multi-frequency device includes first and second groups of electrodes arranged on or in different thickness regions of a single crystal piezoelectric layer, with at least one guided wave confinement structure. Segments of a segmented piezoelectric layer and a segmented layer of electrodes are substantially registered in a device including at least one guided wave confinement structure.
1 . A method of fabricating a micro-electrical-mechanical system (MEMS) guided wave device, the method comprising:
locally thinning a single crystal piezoelectric material layer to define a first thickness region and a second thickness region, wherein a thickness of the first thickness region differs from a thickness of the second thickness region;
depositing a temperature compensation material on a surface of the first thickness region and on a surface of the second thickness region, wherein the temperature compensation material comprises a first temperature compensation layer thickness proximate to the first thickness region, the temperature compensation material comprises a second temperature compensation layer thickness proximate to the second thickness region, and the second temperature compensation layer thickness differs from the first temperature compensation layer thickness;
bonding the locally thinned single crystal piezoelectric material layer on or over an underlying layer to provide a bonded interface;
defining a first plurality of electrodes arranged on or adjacent to the first thickness region and configured for transduction of a lateral acoustic wave having a wavelength 21 in the first thickness region; and
defining a second plurality of electrodes arranged on or adjacent to the second thickness region and configured for transduction of a lateral acoustic wave having a wavelength 22 in the second thickness region.
2 . The method of claim 1 , further comprising planarizing at least one surface of the single crystal piezoelectric material layer prior to the bonding of the locally thinned single crystal piezoelectric material layer on or over the underlying layer.
3 . The method of claim 1 , wherein the first plurality of electrodes comprises a first interdigital transducer, and the second plurality of electrodes defines a second interdigital transducer.
4 . The method of claim 1 , wherein the first plurality of electrodes is substantially coplanar with the second plurality of electrodes.
5 . The method of claim 1 , wherein the first plurality of electrodes is non-coplanar with the second plurality of electrodes.
6 . The method of claim 1 , wherein the underlying layer comprises at least one of a fast wave propagation layer or a Bragg mirror.
7 . The method of claim 1 , wherein the underlying layer comprises a substrate.
8 . The method of claim 1 , wherein the underlying layer comprises a substrate in combination with at least one of a fast wave propagation layer or a Bragg mirror, wherein the at least one of a fast wave propagation layer or a Bragg mirror is arranged between the substrate and the single crystal piezoelectric material layer.
9 . A method of fabricating a micro-electrical-mechanical system (MEMS) guided wave device, the method comprising:
locally thinning a single crystal piezoelectric material layer to define a first thickness region and a second thickness region, wherein a thickness of the first thickness region is greater than a thickness of the second thickness region, the single crystal piezoelectric material layer comprises an upper surface and a lower surface that opposes the upper surface, and the local thinning of the single crystal piezoelectric material layer comprises removing material from the lower surface;
providing a temperature compensation material on a lower surface of the second thickness region, and not on a lower surface of the first thickness region;
bonding the locally thinned single crystal piezoelectric material layer on or over an underlying layer to provide a bonded interface;
defining a first plurality of electrodes on the upper surface on or adjacent to the first thickness region and configured for transduction of a lateral acoustic wave having a wavelength λ 1 in the first thickness region; and
defining a second plurality of electrodes on the upper surface arranged on or adjacent to the second thickness region and configured for transduction of a lateral acoustic wave having a wavelength λ 2 in the second thickness region;
wherein the first plurality of electrodes is substantially coplanar with the second plurality of electrodes.
10 . The method of claim 9 , further comprising planarizing the upper surface of the single crystal piezoelectric material layer prior to the bonding of the locally thinned single crystal piezoelectric material layer on or over the underlying layer.
11 . The method of claim 9 , wherein the first plurality of electrodes comprises a first interdigital transducer, and the second plurality of electrodes defines a second interdigital transducer.
12 . The method of claim 9 , wherein the underlying layer comprises at least one of a fast wave propagation layer or a Bragg mirror.
13 . The method of claim 9 , wherein the underlying layer comprises a substrate.
14 . The method of claim 9 , wherein the underlying layer comprises a substrate in combination with at least one of a fast wave propagation layer or a Bragg mirror, wherein the at least one of a fast wave propagation layer or a Bragg mirror is arranged between the substrate and the single crystal piezoelectric material layer.
15 . The method of claim 9 , further comprising grinding and polishing the upper surface prior to the defining of the first plurality of electrodes and the defining of the second plurality of electrodes.