Piezoelectric micromachined ultrasonic transducer (PMUT)

Patent metadata

Field	Value
Publication number	US-10656255-B2
Application number	US-201615205743-A
Country	US
Kind code	B2
Filing date	Jul 8, 2016
Priority date	May 4, 2016
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

A Piezoelectric Micromachined Ultrasonic Transducer (PMUT) device is provided. The PMUT includes a substrate and an edge support structure connected to the substrate. A membrane is connected to the edge support structure such that a cavity is defined between the membrane and the substrate, where the membrane is configured to allow movement at ultrasonic frequencies. The membrane includes a piezoelectric layer and first and second electrodes coupled to opposing sides of the piezoelectric layer. An interior support structure is disposed within the cavity and connected to the substrate and the membrane.

First claim

What is claimed is:

1. A Piezoelectric Micromachined Ultrasonic Transducer (PMUT) device comprising:
a substrate;
an edge support structure connected to the substrate;
a membrane connected to the edge support structure such that a cavity is defined between the membrane and the substrate, the membrane configured to allow movement at ultrasonic frequencies, the membrane comprising:
a piezoelectric layer configured to generate an electric charge under stress such that the piezoelectric layer senses mechanical vibrations caused by an ultrasonic signal and produces the electric charge responsive to the stress of the piezoelectric layer; and
first and second electrodes coupled to opposing sides of the piezoelectric layer and configured to collect the electric charge; and

an interior support structure disposed within the cavity and connected to the substrate and the membrane, wherein the interior support structure contacts the edge support structure.

2. The PMUT device of claim 1 , further comprising:
a second interior support structure disposed within the cavity and connected to the substrate and the membrane.

3. The PMUT device of claim 1 , wherein the interior support structure is non-centrally positioned within the cavity.

4. The PMUT device of claim 1 , wherein the first electrode defines a continuous layer.

5. The PMUT device of claim 1 , wherein the first electrode is a patterned layer.

6. The PMUT device of claim 1 , the membrane further comprising:
a mechanical support layer connected to the first electrode.

7. The PMUT device of claim 6 , wherein the mechanical support layer defines a continuous layer.

8. The PMUT device of claim 6 , wherein the mechanical support layer is a patterned layer.

9. The PMUT device of claim 1 , wherein the piezoelectric layer defines a continuous layer.

10. The PMUT device of claim 1 , wherein the piezoelectric layer is a patterned layer.

11. The PMUT device of claim 1 , wherein the second electrode extends into the cavity and defines an area between the edge support structure and the interior support structure.

12. The PMUT device of claim 1 , wherein the interior support structure is connected to the piezoelectric layer of the membrane.

13. The PMUT device of claim 1 , wherein the PMUT device is substantially circular such that the edge support structure and the membrane are substantially circular.

14. The PMUT device of claim 1 , wherein the PMUT device is substantially square-shaped such that the edge support structure and the membrane are substantially square-shaped.

15. The PMUT device of claim 1 , wherein at least one of the first electrode and the second electrode is electrically coupled through the interior support structure.

16. The PMUT device of claim 1 , the membrane further comprising:
a third electrode coupled to the piezoelectric layer on an opposing side of the piezoelectric layer as the first electrode.

17. The PMUT device of claim 1 , wherein the edge support structure is connected to an electric potential.

18. The PMUT device of claim 1 , wherein the substrate comprises a CMOS logic wafer.

19. A Piezoelectric Micromachined Ultrasonic Transducer (PMUT) array comprising:
a plurality of PMUT devices, wherein at least one PMUT device of the plurality of PMUT devices comprises:
a substrate;
an edge support structure connected to the substrate, wherein the edge support structure is connected to an electric potential;
a membrane connected to the edge support structure such that a cavity is defined between the membrane and the substrate, the membrane configured to allow movement at ultrasonic frequencies, the membrane comprising:
a piezoelectric layer configured to generate an ultrasonic wave responsive to receiving an electric charge by vibrating in an oscillatory fashion at a frequency related to the electric charge;
first and second electrodes coupled to opposing sides of the piezoelectric layer and configured to apply the electric charge to the piezoelectric layer; and
a mechanical support layer connected to the first electrode; and

an interior support structure disposed within the cavity and connected to the substrate and the membrane, wherein the interior support structure contacts the edge support structure.

20. The PMUT array of claim 19 , wherein the at least one PMUT device of the plurality of PMUT devices further comprises:
a second interior support structure disposed within the cavity and connected to the substrate and the membrane.

21. The PMUT array of claim 19 , wherein the interior support structure is non-centrally positioned within the cavity.

22. The PMUT array of claim 19 , wherein the second electrode extends into the cavity and defines an area between the edge support structure and the interior support structure.

23. The PMUT array of claim 19 , wherein the interior support structure is connected to the piezoelectric layer of the membrane.

24. The PMUT array of claim 19 , wherein at least one of the first electrode and the second electrode is electrically coupled through the interior support structure.

25. The PMUT array of claim 19 , wherein the substrate comprises a CMOS logic wafer.

26. The PMUT array of claim 19 , wherein adjacent PMUT devices of the plurality of PMUT devices are electrically isolated.

27. The PMUT array of claim 19 , wherein groups of adjacent PMUT devices of the plurality of PMUT devices are electrically connected, and wherein adjacent groups of adjacent PMUT devices are electrically isolated.

28. An image sensing system comprising:
a plurality of Piezoelectric Micromachined Ultrasonic Transducer (PMUT) devices, wherein at least one PMUT device of the plurality of PMUT devices comprises:
a substrate;
an edge support structure connected to the substrate;
a membrane connected to the edge support structure such that a cavity is defined between the membrane and the substrate, the membrane configured to allow movement at ultrasonic frequencies, the membrane comprising:
a piezoelectric layer configured to generate a first electric charge under stress such that the piezoelectric layer senses mechanical vibrations caused by an ultrasonic signal and produces the first electric charge responsive to the stress of the piezoelectric layer, and configured to generate an ultrasonic wave responsive to receiving a second electric charge by vibrating in an oscillatory fashion at a frequency related to the second electric charge;
first and second electrodes coupled to opposing sides of the piezoelectric layer, the first and second electrodes configured to collect the first electric charge from the piezoelectric layer and configured to apply the second electric charge to the piezoelectric layer; and
a mechanical support layer connected to the first electrode; and

an interior support structure disposed within the cavity and connected to the substrate and the membrane, wherein the interior support structure contacts the edge support structure; and

control logic electrically coupled to the plurality of PMUT devices, the control logic for sensing an image.

29. The image sensing system of claim 28 , wherein the second electrode extends into the cavity and defines an area between the edge support structure and the interior support structure.

30. The image sensing system of claim 29 , wherein at least one of the f

Assignees

• Invensense Inc

Inventors

• NG Eldwin
• Tsai Julius Ming-Lin
• Apte Nikhil

Classifications

• G01S15/89

  for mapping or imaging · CPC title

• B06B1/0688

  with foil-type piezoelectric elements, e.g. PVDF · CPC title

• A61B8/4483

  characterised by features of the ultrasound transducer · CPC title

• A61B5/1172

  using fingerprinting · CPC title

• G01S7/521 Primary

  Constructional features · CPC title