MEMS ACOUSTIC FILTER AND FABRICATION OF THE SAME

• US 20070046396A1
• Filed: 08/03/2006
• Published: 03/01/2007
• Est. Priority Date: 08/03/2005
• Status: Active Grant

• Current Assignee: Kolo Medical, Ltd.
• Original Assignee: Kolo Technologies, Inc.
• Inventors: Huang, Yongli
• Granted Patent: US 7,612,635 B2
• Time in Patent Office: Days
• US Class Current: 333/186
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: B81C 1/00103 Structures having a predefined profile, e.g. sloped or rounded grooves
• CPC Class Codes: G01N 29/2406 Electrostatic or capacitive probes, e.g. electret or cMUT-probes
• 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: 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

Abstract

A MEMS acoustic filter has a MEMS resonator and 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. Multiple MEMS resonators may be stacked to form a high order acoustic filter. An array of MEMS acoustic filters may be designed to function as an acoustic lens. The MEMS acoustic filter is particularly useful with an ultrasonic transducer, such as PZT and MUT. Fabrication methods to make the same are also disclosed.

Claims

1. A MEMS acoustic filter comprising:

a MEMS resonator; and

at least two acoustic I/O ports.

2. The MEMS acoustic filter of claim 1 wherein the at least two acoustic I/O ports comprises a first I/O port adapted for interfacing with a medium, and a second I/O port adapter for interfacing with an acoustic transducer.

3. The MEMS acoustic filter of claim 1 wherein the MEMS resonator is passive.

4. The MEMS acoustic filter of claim 1 wherein the MEMS resonator is active.

5. The MEMS acoustic filter of claim 1 wherein the MEMS resonator is a first-order resonator.

6. The MEMS acoustic filter of claim 1 wherein the MEMS resonator is a higher-order resonator.

7. The MEMS acoustic filter of claim 1 wherein the MEMS resonator comprises a higher-order resonator having a plurality of first-order resonators.

8. The MEMS acoustic filter of claim 1 wherein the MEMS resonator comprises a higher-order resonator having a plurality of first-order resonators stacked on one another.

9. The MEMS acoustic filter of claim 1 wherein the MEMS resonator comprises a first resonator and a second resonator, the first resonator having a first I/O port adapted for being attached to an ultrasound transducer, and the second resonator having a second I/O port adapted for interfacing with a medium.

10. The MEMS acoustic filter of claim 9 wherein the first resonator having a third I/O port, and the second resonator having a fourth I/O port, the third I/O port and the fourth I/O port being directly or indirectly connected together.

11. The MEMS acoustic filter of claim 1 wherein the MEMS resonator comprises:

a flexible membrane layer;

a least one connector; and

a base layer, wherein a bottom surface of the flexible membrane layer is connected to the base layer through the at least one connector.

12. The MEMS acoustic filter of claim 11 wherein the at least two I/O ports comprise a first I/O port and a second I/O port, the flexible membrane layer has a top surface adapted for serving as at least a part of the first I/O port, and the base layer has a bottom surface adapted for serving as at least a part of the second I/O port.

13. The MEMS acoustic filter of claim 11 wherein the flexible membrane layer comprises a first electrode, and the base layer comprises a second electrode.

14. The MEMS acoustic filter of claim 1 wherein the MEMS resonator 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.

15. The MEMS acoustic filter of claim 14 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.

16. The MEMS acoustic filter of claim 14 wherein the at least two I/O ports comprise a first I/O port and a second I/O port, the mass layer has a top surface adapted for serving as at least a part of the first I/O port, and the base layer has a bottom surface adapted for serving as at least a part of the second I/O port.

17. The MEMS acoustic filter of claim 14 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.

18. The MEMS acoustic filter of claim 1 which is attached to a micromachined ultrasonic transducer (MUT) element.

19. The MEMS acoustic filter of claim 1 which is attached to a micromachined ultrasonic transducer (MUT) element through a bonding interface layer.

20. The MEMS acoustic filter of claim 1 which is attached to a capacitive micromachined ultrasonic transducer (cMUT) element.

21. The MEMS acoustic filter of claim 1 which is attached to a piezoelectric micromachined ultrasonic transducer (pMUT) element.

22. The MEMS acoustic filter of claim 1 which is attached to a magnetic micromachined ultrasonic transducer (mMUT) element.

23. The MEMS acoustic filter of claim 1 which is attached to a piezoelectric transducer (PZT).

24. An ultrasonic transducer comprising:

an ultrasonic transducer element; and

a MEMS acoustic filter attached to the ultrasonic transducer element.

25. The ultrasonic transducer of claim 24 wherein the MEMS acoustic filter comprises a MEMS resonator.

26. The ultrasonic transducer of claim 24 wherein the MEMS acoustic filter comprises a first MEMS resonator and a second MEMS resonator stacked together.

27. The ultrasonic transducer of claim 26 wherein the first MEMS resonator is attached to a back end of the ultrasonic transducer element to connect to a substrate, and the second MEMS resonator is attached to a front end of the ultrasonic transducer to interface with a medium.

28. The ultrasonic transducer of claim 24 wherein the ultrasonic transducer element comprises a capacitive transducing member.

29. The ultrasonic transducer of claim 24 wherein the ultrasonic transducer element comprises a piezoelectric transducing member.

30. The ultrasonic transducer of claim 24 wherein the MEMS acoustic filter comprises:

a MEMS resonator; and

at least two acoustic I/O ports.

31. An ultrasonic transducer array comprising:

an array of ultrasonic transducer elements; and

an array of MEMS acoustic filters each attached to a respective one of the array of ultrasonic transducer elements.

32. The ultrasonic transducer array of claim 31 wherein the array of MEMS acoustic filters is each characterized by a phase factor, at least two of the array of MEMS acoustic filters having different phase factors.

33. The ultrasonic transducer of claim 31 wherein the array of MEMS acoustic filters have a pattern of phase factors arranged such that the array of MEMS acoustic filters function as an acoustic lens assisting focusing an acoustic beam to form an acoustic image.

34. The ultrasonic transducer of claim 31 wherein the array of MEMS acoustic filters each comprises a MEMS resonator.

35. A method for fabricating a MEMS acoustic filter, the method comprising:

depositing and patterning a first sacrificial layer on a substrate;

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

depositing and patterning a second sacrificial layer;

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

removing the first and the second sacrificial layers, such that the first structure layer forms an anchor layer, and the second structure layer forms the spring layer defining a cantilever anchored on the anchor layer.

36. The method of claim 35 further comprising:

depositing and patterning a third sacrificial layer; and

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

37. A method for fabricating an ultrasonic transducer having a MEMS acoustic filter, the method comprising the steps of:

forming a MEMS resonator on a substrate;

bonding an ultrasonic transducer element to the MEMS resonator; and

removing the substrate from the MEMS resonator.

38. The method of claim 37 wherein the step of forming the MEMS resonator on the substrate comprises:

depositing and patterning a first sacrificial layer;

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

depositing and patterning a second sacrificial layer;

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

removing the first and the second sacrificial layers, such that the first structure layer forms an anchor layer, and the second structure layer forms the spring layer defining a cantilever anchored on the anchor layer.

39. The method of claim 38 further comprising:

depositing and patterning a third sacrificial layer; and

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

40. A method for fabricating an ultrasonic transducer, the method comprising the steps of:

forming an ultrasonic transducer element on a substrate, wherein the ultrasonic transducer element has a top surface plate; and

forming a MEMS resonator on the top surface plate of the ultrasonic transducer element.

41. The method of claim 40 wherein the step of forming the MEMS resonator on the top surface plate comprises:

depositing and patterning a first sacrificial layer;

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

depositing and patterning a second sacrificial layer;

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

removing the first and the second sacrificial layers, such that the first structure layer forms an anchor layer, and the second structure layer forms the spring layer defining a cantilever anchored on the anchor layer.