MEMS ultrasonic device having a PZT and cMUT

• US 8,004,373 B2
• Filed: 10/06/2009
• Issued: 08/23/2011
• Est. Priority Date: 08/03/2005
• Status: Active Grant

• Current Assignee: Kolo Medical, Ltd.
• Original Assignee: Kolo Technologies, Inc.
• Inventors: Huang, Yongli
• Primary Examiner(s): Tran; Anh Q
• Application Number:
  US12/574,504
• Publication Number:
  US 20100207489A1
• Time in Patent Office: 686 Days
• Field of Search: None
• US Class Current: 333/186
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: B81B 3/0027 Structures for transforming mechanical energy, e.g. potential energy of a spring into translation, sound into translation
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 1/00182 Arrangements of deformable or non-deformable structures, e.g. membrane and cavity for use in a transducer
• CPC Class Codes: B81C 1/00357 involving bonding one or several substrates on a non-temporary support, e.g. another substrate
• CPC Class Codes: B81C 1/00373 Selective deposition, e.g. printing or microcontact printing
• CPC Class Codes: B81C 1/00523 Etching material
• CPC Class Codes: B81C 1/00626 Processes for achieving a desired geometry not provided for in groups B81C1/00563 - B81C1/00619
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H02N 1/006 of the gap-closing type H02N1/004 takes precedence
• CPC Class Codes: H03H 3/0072 of microelectro-mechanical resonators or networks micromembranes or microbeams B81B2203/01; manufacture of microstructural devices in general B81C
• CPC Class Codes: H03H 9/02259 Driving or detection means
• CPC Class Codes: H03H 9/2405 of microelectro-mechanical resonators
• CPC Class Codes: H03H 9/462 Microelectro-mechanical filters
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 2201/003 Mems transducers or their use
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer

Abstract

A MEMS ultrasonic device has an array of PZT transducer elements and a cMUT structure bonded to the array of PZT transducer elements. The MEMS ultrasonic device can be adapted for ultrasonic imaging. The cMUT structure may serve as an active MEMS acoustic filter having at least two acoustic I/O ports to alter an input acoustic signal to an output acoustic signal. The first I/O port is adapted for interfacing with a medium, and the second I/O port for passing an acoustic signal to an acoustic transducer. An array of MEMS acoustic filters may be designed to function as an acoustic lens. Fabrication methods to make the same are also disclosed.

Claims

1. A MEMS ultrasonic device comprising:

a PZT transducer; and

a cMUT structure bonded to the PZT transducer.

2. The MEMS ultrasonic device as recited in claim 1 adapted for ultrasonic imaging.

3. The MEMS ultrasonic device as recited in claim 1, further comprising a lens layer adapted for focusing an ultrasonic beam.

4. The MEMS ultrasonic device as recited in claim 1, wherein the cMUT structure is bonded to the PZT transducer through a contact layer.

5. The MEMS ultrasonic device as recited in claim 1, further comprising at least two acoustic I/O ports.

6. The MEMS ultrasonic device as recited in claim 1, wherein the cMUT structure comprises:

a flexible membrane layer having a top surface adapted for serving as at least a part of a first acoustic I/O port;

a least one connector; and

a base layer connected to the flexible membrane layer through the at least one connector, the base layer having a bottom surface adapted for serving as at least a part of the second I/O port.

7. The MEMS ultrasonic device as recited in claim 1, wherein the cMUT structure comprises:

a flexible membrane layer having a first electrode; and

a base layer having a second electrode, the base layer being connected to the flexible membrane layer through the at least one connector.

8. The MEMS ultrasonic device as recited in claim 1, wherein the cMUT structure comprises:

a mass layer;

a spring layer; and

a base layer, wherein the mass layer has a bottom surface connected to a top surface of the spring layer through a spring-mass connector, and the spring membrane is connected to the base layer.

9. The MEMS ultrasonic device as recited in claim 8, wherein the mass layer is connected to the spring layer through a plurality of spring-mass connectors, and the spring layer is connected to the base layer through a plurality of spring anchors, the plurality of spring anchors being disposed in intervals of the plurality of spring-mass connectors.

10. The MEMS ultrasonic device as recited in claim 8, wherein one of the mass layer and spring layer comprises a first electrode, and one of the spring layer or the base layer comprises a second electrode.

11. The MEMS ultrasonic device as recited in claim 1, wherein the cMUT structure is adapted to serve as an acoustic matching layer to the PZT transducer.

12. The MEMS ultrasonic device as recited in claim 1, wherein the PZT transducer comprises an array of PZT transducer elements.

13. The MEMS ultrasonic device as recited in claim 12, wherein the array of PZT transducer elements have nonuniform sizes and/or nonuniform locations, and the cMUT structure is adapted to serve as an acoustic matching layer to the array of PZT transducer elements to reduce an effective the nonuniform sizes and/or nonuniform locations.

14. The MEMS ultrasonic device as recited in claim 1, wherein the cMUT structure comprises an array of cMUT resonators.

15. The MEMS ultrasonic device as recited in claim 14, wherein the PZT transducer comprises an array of PZT transducer elements, and wherein the cMUT resonators are each attached to a respective one of the array of PZT transducer elements.

16. The MEMS ultrasonic device as recited in claim 1, wherein the cMUT structure comprises a thin base layer.

17. The MEMS ultrasonic device as recited in claim 1, wherein the cMUT structure comprises one or more active cMUT resonators having an electric field applied thereupon.

18. A method for fabricating an ultrasonic transducer, the method comprising:

forming a cMUT structure on a substrate;

bonding PZT transducer to the cMUT structure; and

removing the substrate from the cMUT structure.

19. The method of claim 18 wherein forming the cMUT structure on the substrate comprises:

depositing and patterning a first sacrificial layer;

depositing and patterning a first structure layer over the first sacrificial layer; and

removing the first sacrificial layers, such that the first structure layer forms membrane layer.

20. The method of claim 19 further comprising:

depositing and patterning a second sacrificial layer; and

depositing and patterning a second structure layer over the second sacrificial layer, such that the second structure layer forms a plate layer above the membrane layer.