Acoustic resonator with reduced mechanical clamping of an active region for enhanced shear mode response

Patent metadata

Field	Value
Publication number	US-10326425-B2
Application number	US-201615357006-A
Country	US
Kind code	B2
Filing date	Nov 21, 2016
Priority date	Nov 20, 2015
Publication date	Jun 18, 2019
Grant date	Jun 18, 2019

Abstract

The present disclosure provides an acoustic resonator with reduced mechanical clamping of an active region for enhanced shear mode response. More specifically, the present disclosure provides a solidly mounted BAW resonator device with an active region of piezoelectric material laterally surrounded by an inactive region with a reduced thickness of piezoelectric material such that at least an upper portion of the inactive region along a boundary of the active region is devoid of piezoelectric material. The resonator device provides a discontinuity along opposing lateral edges of the piezoelectric material of the active region to reduce mechanical clamping of the active region in a direction of maximum lateral displacement in shear mode operation. Increasing the mechanical isolation of the active region of piezoelectric material decreases mechanical damping of lateral vibrations of the active region which enhances the shear mode response for quasi-shear mode sensing.

First claim

What is claimed is:

1. A micro-electrical-mechanical system (MEMS) resonator device comprising:
a substrate; and
a bulk acoustic wave resonator structure arranged over at least a portion of the substrate, the bulk acoustic wave resonator structure including a piezoelectric material comprising a c-axis having an orientation distribution that is predominantly non-parallel to normal of a face of the substrate, a top side electrode arranged over the piezoelectric material, and a bottom side electrode arranged between the piezoelectric material and the substrate, wherein at least a portion of the piezoelectric material is arranged between the top side electrode and the bottom side electrode to form an active region;
wherein the active region is laterally surrounded by an inactive region, and a thickness of piezoelectric material of at least a portion of the inactive region is less than a thickness of piezoelectric material of the active region, such that at least an upper portion of the inactive region along a boundary of the active region is devoid of piezoelectric material, defining at least one discontinuity along at least upper portions of opposing lateral edges of piezoelectric material of the active region, wherein the at least one discontinuity is configured to reduce mechanical clamping of the active region in a direction of maximum lateral displacement in shear mode operation of the bulk acoustic wave resonator structure; wherein the active region comprises a length parallel to the direction of maximum lateral displacement in shear mode operation of the bulk acoustic wave resonator structure, and the active region comprises a width perpendicular to the length, wherein the length extends between a first lengthwise end and a second lengthwise end of the active region; and wherein the length is greater than the width.

2. The MEMS resonator device of claim 1 , wherein:
the at least a portion of the piezoelectric material arranged between the top side electrode and the bottom side electrode comprises a nominal thickness; and
at least a portion of a lateral perimeter of the active region is bounded by a reduced thickness portion of the piezoelectric material having a thickness in a range of from 0% to about 50% of the nominal thickness.

3. The MEMS resonator device of claim 1 , wherein:
the at least one discontinuity is bounded at least in part by the first lengthwise end and the second lengthwise end.

4. The MEMS resonator device of claim 1 , wherein the at least one discontinuity surrounds at least about 60% of a perimeter of the active region.

5. The MEMS resonator device of claim 1 , wherein the bulk acoustic wave resonator structure comprises an acoustic reflector structure arranged between the substrate and the bottom side electrode.

6. The MEMS resonator device of claim 1 , wherein the substrate defines a recess, and a support layer is arranged between the recess and the bulk acoustic wave resonator structure.

7. The MEMS resonator device of claim 1 , wherein a hermeticity layer is arranged over at least a portion of at least one of: the top side electrode, the bottom side electrode, or at least one lateral edge of the active region.

8. The MEMS resonator device of claim 1 , wherein:
the piezoelectric material comprises at least one anchor portion extending in a direction perpendicular to the length of the active region, and contacting the active region midway between lengthwise ends of the active region.

9. The MEMS resonator device of claim 8 , wherein at least a portion of at least one of the top side electrode or the bottom side electrode extends along the at least one anchor portion of the piezoelectric material.

10. The MEMS resonator device of claim 1 , further comprising a dielectric material arranged over lateral edges of the active region.

11. A fluidic device comprising:
the MEMS resonator device of claim 1 ;
at least one functionalization material arranged over at least a portion of the active region; and
a fluidic channel containing the active region.

12. A method for biological or chemical sensing, the method comprising:
supplying a fluid containing a target species into the fluidic channel of the fluidic device of claim 11 , wherein said supplying is configured to cause at least some of the target species to bind to the at least one functionalization material;
inducing a bulk acoustic wave in the active region; and
sensing a change in at least one of a frequency property, an amplitude magnitude property, or a phase property of the bulk acoustic wave resonator structure to indicate at least one of presence or quantity of target species bound to the at least one functionalization material.

13. The fluidic device of claim 11 , wherein the at least one functionalization material comprises at least one of a specific binding material or a non-specific binding material.

14. The fluidic device of claim 11 , further comprising a self-assembled monolayer arranged between the at least one functionalization material and the top side electrode.

15. The fluidic device of claim 14 , further comprising an interface layer arranged between the top side electrode and the self-assembled monolayer.

16. A method for fabricating a micro-electrical-mechanical system (MEMS) resonator device, the method comprising:
forming a base structure including a substrate, a piezoelectric material arranged over at least a portion of the substrate and comprising a c-axis having an orientation distribution that is predominantly non-parallel to normal of a face of the substrate, and a bottom side electrode arranged between the substrate and at least a portion of the piezoelectric material, wherein the piezoelectric material comprises a nominal thickness;
removing a portion of the piezoelectric material to define a reduced thickness portion of the piezoelectric material having a thickness in a range of from 0% to about 50% of the nominal thickness;
forming a top side electrode over a portion of the piezoelectric material, wherein at least a portion of the piezoelectric material comprising the nominal thickness is arranged between the top side electrode and the bottom side electrode to form an active region of a bulk acoustic wave resonator structure; and
depositing a hermeticity layer over at least a portion of at least one of: the top side electrode, the bottom side electrode, or at least one lateral edge of the active region,
wherein at least a portion of a lateral perimeter of the active region is bounded by the reduced thickness portion of the piezoelectric material, defining at least one discontinuity configured to reduce mechanical clamping of the active region in a direction of maximum lateral displacement in shear mode operation of the bulk acoustic wave resonator structure.

17. The method of claim 16 , further comprising forming a self-assembled monolayer over at least a portion of the top side electrode, and applying at least one functionalization material over at least a portion of the self-assembled monolayer, wherein at least a portion of the at least one functionalization material is registered with the active region.

18. A micro-electrical-mechanical system (MEMS) resonator device comprising:
a substrate; and
a bulk acoustic wave resonator structure arranged over at least a portion of the substrate, the bulk acoustic wave resonator structure including a piezoelectric material comprising a c-axis having an orientation distribution that is predominantly non-parallel to normal of a face of the substrate, a top side electrode arranged over the piezoel

Assignees

• Qorvo Us Inc

Inventors

• Belsick John
• Morton Rick

Classifications

• G01N2291/0255

  (Bio)chemical reactions, e.g. on biosensors · CPC title

• G01N2291/0422

  Shear waves, transverse waves, horizontally polarised waves · CPC title

• G01N29/036

  by measuring frequency or resonance of acoustic waves · CPC title

• H03H2009/155

  using MEMS techniques · CPC title

• H03H9/172

  Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume · CPC title