Multi-frequency guided wave devices and fabrication methods

Patent metadata

Field	Value
Publication number	US-2016182008-A1
Application number	US-201514972929-A
Country	US
Kind code	A1
Filing date	Dec 17, 2015
Priority date	Dec 17, 2014
Publication date	Jun 23, 2016
Grant date	—

Abstract

A micro-electrical-mechanical system (MEMS) guided wave device includes a piezoelectric layer including multiple thinned regions of different thicknesses each bounding in part a different recess, different groups of electrodes on or adjacent to different thinned regions and arranged for transduction of lateral acoustic waves of different wavelengths in the different thinned regions, and at least one bonded interface between the piezoelectric layer and a substrate. Optionally, a buffer layer may be intermediately bonded between the piezoelectric layer and the substrate. Methods of producing such devices include locally thinning a piezoelectric layer to define multiple recesses, bonding the piezoelectric layer on or over a substrate layer to cause the recesses to be bounded in part by either the substrate or an optional buffer layer, and defining multiple groups of electrodes on or over the different thinned regions.

First claim

What is claimed is:

1 . A micro-electrical-mechanical system (MEMS) guided wave device comprising:
a piezoelectric layer including a first recess bounded in part by a first thinned region of the piezoelectric layer comprising a first thickness, and including a second recess bounded in part by a second thinned region of the piezoelectric layer comprising a second thickness, wherein the second thickness differs from the first thickness; a first plurality of electrodes arranged on or adjacent to the first thinned region and configured for transduction of a lateral acoustic wave having a wavelength λ 1 in the first thinned region; a second plurality of electrodes arranged on or adjacent to the second thinned region and configured for transduction of a lateral acoustic wave having a wavelength λ 2 in the second thinned region; a substrate layer arranged on or adjacent to the piezoelectric layer; and a bonded interface between the piezoelectric layer and the substrate layer.

2 . The MEMS guided wave device of claim 1 , further comprising a buffer layer arranged between the piezoelectric layer and the substrate layer along the bonded interface, wherein the first recess and the second recess are bounded in part by the buffer layer.

3 . The MEMS guided wave device of claim 1 , further comprising a field layer intermediately arranged between the piezoelectric layer and the substrate layer, wherein the field layer defines a first field layer aperture substantially registered with the first recess and defines a second field layer aperture substantially registered with the second recess.

4 . The MEMS guided wave device of claim 1 , wherein at least one of the first recess or the second recess comprises an unfilled cavity.

5 . The MEMS guided wave device of claim 1 , wherein at least one of the first recess or the second recess is filled with a fast wave propagation material or a slow wave propagation material.

6 . The MEMS guided wave device of claim 1 , wherein:
the substrate layer defines a first substrate recess and a second substrate recess; the first substrate recess is substantially registered with the first recess; and the second substrate recess is substantially registered with the second recess.

7 . The MEMS guided wave device of claim 6 , wherein at least one of the first recess; the second recess, the first substrate recess, or the second substrate recess comprises an unfilled cavity.

8 . The MEMS guided wave device of claim 1 , wherein the first plurality of electrodes includes a first interdigital transducer (IDT) comprising a first two groups of electrodes of opposing polarity and comprising a first spacing between adjacent electrodes of opposing polarity of the first two groups of electrodes of opposing polarity; the second plurality of electrodes includes a second interdigital transducer (IDT) comprising a second two groups of electrodes of opposing polarity and comprising a second spacing between adjacent electrodes of opposing polarity of the second two groups of electrodes of opposing polarity; and the second spacing differs from the first spacing.

9 . The MEMS guided wave device of claim 1 , comprising one or both of the following features (i) and (ii): (i) the first plurality of electrodes comprises at least one electrode arranged within the first recess; and (ii) the second plurality of electrodes comprises at least one electrode arranged within the second recess.

10 . The MEMS guided wave device of claim 1 , further comprising a first anchor and a second anchor, wherein at least a portion of the piezoelectric layer including the first thinned region and the second thinned region is suspended between the first anchor and the second anchor.

11 . The MEMS guided wave device of claim 1 , wherein piezoelectric material of the piezoelectric layer comprises single crystal piezoelectric material.

12 . The MEMS guided wave device of claim 1 , wherein the piezoelectric layer is devoid of ion implantation affected regions.

13 . A method of fabricating a MEMS guided wave device, the method comprising:
locally thinning a piezoelectric layer to define a first recess and a second recess in the piezoelectric layer, wherein the first recess is bounded by a first thinned region of the piezoelectric layer comprising a first thickness, the second recess is bounded by a second thinned region of the piezoelectric layer comprising a second thickness, and the second thickness differs from the first thickness; bonding the piezoelectric layer on or over a substrate layer, to form at least one bonded interface between the piezoelectric layer and the substrate layer; defining a first plurality of electrodes arranged on or adjacent to the first thinned region and configured for transduction of a lateral acoustic wave having a wavelength λ 1 in the first thinned region; and defining a second plurality of electrodes arranged on or adjacent to the second thinned region and configured for transduction of a lateral acoustic wave having a wavelength λ 2 in the second thinned region.

14 . The method of claim 13 , further comprising:
depositing a sacrificial material in the first recess and the second recess prior to the bonding; planarizing at least one surface of the piezoelectric layer after deposition of the sacrificial material; and removing the sacrificial material from the first recess and the second recess after the bonding.

15 . The method of claim 13 , further comprising:
filling at least one of the first recess or the second recess with a fast wave propagation material prior to the bonding; and prior to the bonding, planarizing at least one surface of the piezoelectric layer after filling of at least one of the first recess or the second recess.

16 . The method of claim 13 , further comprising thinning and polishing at least one surface of the piezoelectric layer after the bonding.

17 . The method of claim 13 , comprising at least one of the following features (i) or (ii):
(i) the defining of the first plurality of electrodes includes defining at least one electrode within the first recess; and (ii) the defining of the second plurality of electrodes includes defining at least one electrode within the second recess.

18 . The method of claim 13 , further comprising depositing a buffer layer on one of the piezoelectric layer or the substrate layer, wherein the bonding of the piezoelectric layer on or over the substrate layer comprises bonding the other of the piezoelectric layer or the substrate layer to the buffer layer, to cause the first recess and the second recess to be bounded in part by the buffer layer.

19 . The method of claim 14 , further comprising:
defining a first substrate recess and a second substrate recess in the substrate layer prior to the bonding; planarizing at least one surface of the substrate layer after deposition of the sacrificial material; and positioning the piezoelectric layer and the substrate layer relative to one another to substantially register the first substrate recess with the first recess, and to substantially register the second substrate recess with the second recess, prior to the bonding.

20 . The method of claim 13 , further comprising:
depositing sacrificial material in the first recess and the second recess; forming a composite layer including field layer regions and including first and second sacrificial material regions over the substrate layer; planarizing at least one surface of the piezoelectric layer and at least o

Assignees

• Rf Micro Devices Inc

Inventors

• Bhattacharjee Kushal

Classifications

• H03H9/02228

  Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer · CPC title

• H03H9/02275 Primary

  Comb electrodes · CPC title

• H03H3/02

  for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) · CPC title

• H03H9/02244 Primary

  of microelectro-mechanical resonators · CPC title

• H03H2003/027

  the resonators or networks being of the microelectro-mechanical [MEMS] type · CPC title