CMUTS WITH A HIGH-K DIELECTRIC

• US 20100202254A1
• Filed: 07/31/2008
• Published: 08/12/2010
• Est. Priority Date: 07/31/2007
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Roest, Aarnoud Laurens, Klee, Mareike, Van Beek, Jozef Thomas Martinus, Reimann, Klaus, Fraser, John Douglas
• Granted Patent: US 8,203,912 B2
• Time in Patent Office: Days
• US Class Current: 367/180
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type

Abstract

A capacitive ultrasound transducer includes a first electrode, a second electrode, and a third electrode, the third electrode including a central region disposed in collapsibly spaced relation with the first electrode, and a peripheral region disposed outward of the central region and disposed in collapsibly spaced relation with the second electrode. The transducer further includes a layer of a high dielectric constant material disposed between the third electrode and the first electrode, and between the third electrode and the second electrode. The transducer may be operable in a collapsed mode wherein the peripheral region of the third electrode oscillates relative to the second electrode, and the central region of the third electrode is fully collapsed with respect to the first electrode such that the dielectric layer is sandwiched therebetween. Piezoelectric actuation, such as d31 and d33 mode piezoelectric actuation, may further be included. A medical imaging system includes an array of such capacitive ultrasound transducers disposed on a common substrate.

Claims

1. A capacitive ultrasound transducer, comprising:

a first electrode;

a second electrode;

a third electrode, the third electrode including a central region disposed in collapsibly spaced relation with the first electrode, and a peripheral region disposed outward of the central region and disposed in collapsibly spaced relation with the second electrode; and

a layer of a high dielectric constant material disposed between the third electrode and the first electrode and between the third electrode and the second electrode.

2. A capacitive ultrasound transducer in accordance with claim 1, wherein the capacitive ultrasound transducer is operable in a collapsed mode wherein the peripheral region of the third electrode oscillates relative to the second electrode, and the central region of the third electrode is fully collapsed with respect to the first electrode such that the layer of a high dielectric constant material is sandwiched therebetween.

3. A capacitive ultrasound transducer in accordance with claim 1, wherein the layer of a high dielectric constant material is disposed in collapsibly spaced relation with each of the first and second electrodes.

4. A capacitive ultrasound transducer in accordance with claim 3, wherein the layer of a high dielectric constant material and the third layer are affixed to each other.

5. A capacitive ultrasound transducer in accordance with claim 1, wherein the layer of a high dielectric constant material is affixed to the first and second electrodes such that the central and peripheral regions of the third electrode are further in collapsibly spaced relation with the layer of a high dielectric constant material.

6. A capacitive ultrasound transducer in accordance with claim 1, further including a piezoelectric layer and a fourth electrode, and wherein the third and fourth electrodes are cooperative for applying an electric field to the piezoelectric layer.

7. A capacitive ultrasound transducer in accordance with claim 6, wherein each of the third and fourth electrodes is affixed to the layer of a high dielectric constant material.

8. A capacitive ultrasound transducer in accordance with claim 7, wherein the layer of a high dielectric constant material is sandwiched between the third and fourth electrodes and forms at least a portion of the piezoelectric layer.

9. A capacitive ultrasound transducer in accordance with claim 8, wherein the third and fourth electrodes are cooperative for producing d31 mode piezoelectric coupling with respect to the piezoelectric layer.

10. A capacitive ultrasound transducer in accordance with claim 7, wherein the third and fourth electrodes are disposed along a common side of the layer of a high dielectric constant material.

11. A capacitive ultrasound transducer in accordance with claim 10, wherein the third and fourth electrodes are interdigitated.

12. A capacitive ultrasound transducer in accordance with claim 10, wherein the third and fourth electrodes are cooperative for producing d33 mode piezoelectric coupling with respect to the piezoelectric layer.

13. A capacitive ultrasound transducer in accordance with claim 1, wherein the dielectric constant of the high dielectric constant material layer has a value of at least 100.

14. A capacitive ultrasound transducer in accordance with claim 1, further comprising a fourth electrode, wherein the second electrode is disposed between the first electrode and the fourth electrode, and the third electrode further includes another peripheral region disposed outward of the central region and disposed in collapsibly spaced relation with the fourth electrode, and wherein the layer of a high dielectric constant material is further disposed between the third electrode and the fourth electrode.

15. A medical imaging system comprising a capacitive ultrasound transducer in accordance with claim 1.

16. A medical imaging system comprising an array of capacitive ultrasound transducers in accordance with claim 1 disposed on a common substrate.

17. A method of operating a capacitive ultrasound transducer, comprising:

providing a capacitive ultrasound transducer including a first electrode, a second electrode, a third electrode in collapsibly spaced relation with respect to each of the first and second electrodes, and a layer of a high dielectric constant material disposed between the third electrode and the first electrode, and between the third electrode and the second electrode;

collapsing a central region of the third electrode with respect to the first electrode such that the layer of a high dielectric constant material is sandwiched therebetween; and

oscillating, with respect to the second electrode, a peripheral region of the third electrode disposed outward of the central region.

18. A method of operating a capacitive ultrasound transducer in accordance with claim 17, wherein the capacitive ultrasound transducer further comprises a piezoelectric layer and a fourth electrode, and the method further comprises cooperatively employing the third and fourth electrodes to produce piezoelectric coupling with respect to the piezoelectric layer.

19. A method of operating a capacitive ultrasound transducer in accordance with claim 18, further comprising utilizing the piezoelectric coupling to calibrate at least one selected from a group comprising a gap, a stiffness, and a performance of the capacitive ultrasound transducer.

20. A method of operating a capacitive ultrasound transducer in accordance with claim 18, further comprising utilizing the piezoelectric coupling to support a capacitive actuation of the capacitive ultrasound transducer.

21. A method of operating a capacitive ultrasound transducer in accordance with claim 18, wherein the piezoelectric coupling includes d33 mode piezoelectric coupling.

22. A method of operating a capacitive ultrasound transducer in accordance with claim 18, wherein the piezoelectric coupling includes d31 mode piezoelectric coupling.