PIEZOELECTRIC MICROMACHINED ULTRASOUND TRANSDUCER WITH PATTERNED ELECTRODES

• US 20130278111A1
• Filed: 03/15/2013
• Published: 10/24/2013
• Est. Priority Date: 04/19/2012
• Status: Abandoned Application

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Masdar Institute Of Science And Technology, Massachusetts Institute of Technology
• Inventors: Sammoura, Firas, Smyth, Katherine Marie, Kim, Sang-Gook
• Application Number:
  US13/833,159
• Publication Number:
  US 20130278111A1
• Time in Patent Office: Days
• US Class Current: 310/317
• CPC Class Codes: B06B 1/0622 on one surface
• CPC Class Codes: B06B 1/0625 Annular array
• CPC Class Codes: B06B 1/0629 Square array
• CPC Class Codes: H10N 30/20 with electrical input and mechanical output, e.g. functioning as actuators or vibrators
• CPC Class Codes: H10N 30/204 using bending displacement, e.g. unimorph, bimorph or multimorph cantilever or membrane benders
• CPC Class Codes: H10N 30/87 Electrodes or interconnections, e.g. leads or terminals

Abstract

A piezoelectric micro-machined ultrasonic transducer (PMUT) uses multiple electrodes, e.g., in a radial pattern for a disc, to improve performance. The multiple electrodes may be differentially driven to operate the PMUT in d₃₁ mode (that is, with an applied electrical field perpendicular to the piezoelectrically-induced strain) where deflection relative to input voltage is increased and in-plane stresses are reduce, thus improving overall performance.

Claims

1. A device formed of a clamped, micromachined structure, the device comprising:

a piezoelectric material having a top surface and a bottom surface;

a first group of electrodes forming a pattern on the top surface of the first piezoelectric material; and

a second group of electrodes forming the pattern on the bottom surface of the first piezoelectric material.

2. The device of claim 1 wherein the piezoelectric material is a disc.

3. The device of claim 2 wherein the first group of electrodes includes a first electrode having a circular shape centered on the disc.

4. The device of claim 1 wherein the piezoelectric material has a perimeter shape selected from a group consisting of a square and a hexagon.

5. The device of claim 1 wherein the first group of electrodes forms a number of concentric rings separated by a corresponding number of gaps.

6. The device of claim 1 wherein the first group of electrodes includes three or more electrodes.

7. The device of claim 6 further comprising a voltage source configured to drive each one of the three or more electrodes at a substantially different voltage.

8. The device of claim 6 further comprising a voltage source that drives at least two of the three or more electrodes at a substantially equal voltage.

9. The device of claim 8 wherein the substantially equal voltage is about zero Volts.

10. The device of claim 1 further comprising a voltage source configured to differentially drive adjacent ones of the first group of electrodes.

11. The device of claim 1 further comprising a voltage source configured to differentially drive one of the first group of electrodes and an opposing one of the second group of electrodes.

12. The device of claim 1 wherein the piezoelectric material is not initially poled.

13. The device of claim 1 wherein the piezoelectric material is poled Aluminum nitride.

14. The device of claim 1 further comprising a silicon substrate.

15. The device of claim 1 wherein the clamped, micromachined structure includes a support structure.

16. The device of claim 1 wherein the piezoelectric material includes a Lead Zirconate Titanate (PZT).

17. The device of claim 1 wherein the PZT is Perovskite-phase PZT.

18. The device of claim 1 wherein the piezoelectric material includes a piezoelectric ceramic bulk material.

19. The device of claim 1 wherein the clamped, micromachined structure is an ultrasound transducer having a resonant frequency of between one and eighteen Megahertz.

20. The device of claim 1 wherein the first group of electrodes covers about thirty-six percent of a top area of the piezoelectric material.

21. The device of claim 1 wherein the first group of electrodes cover about sixty percent of a radius of the piezoelectric material.

22. The device of claim 1 further comprising:

a second piezoelectric material having a second top surface and a second bottom surface, the second top surface adjacent to the second group of electrodes; and

a third group of electrodes forming the pattern on the second bottom surface of the second piezoelectric material.

23. The device of claim 22 further comprising a voltage source that drives one of the third group of electrodes and a corresponding one of the first group of electrodes at a substantially equal voltage.