Micro-electro-mechanical transducer having a surface plate

• US 8,018,301 B2
• Filed: 01/31/2011
• Issued: 09/13/2011
• 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:
  US13/018,162
• Publication Number:
  US 20110136284A1
• Time in Patent Office: 225 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 of the electrostatic type H04R19/005
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer

Abstract

A micro-electro-mechanical transducer (such as a cMUT) is disclosed. The transducer has a base, a spring layer placed over the base, and a mass layer connected to the spring layer through a spring-mass connector. The base includes a first electrode. The spring layer or the mass layer includes a second electrode. The base and the spring layer form a gap therebetween and are connected through a spring anchor. The mass layer provides a substantially independent spring mass contribution to the spring model without affecting the equivalent spring constant. The mass layer also functions as a surface plate interfacing with the medium to improve transducing performance. Fabrication methods to make the same are also disclosed.

Claims

1. A method for fabricating a micro-electro-mechanical device having a movable mechanical part to transform energy, the method comprising the steps of:

forming at least one spring anchor on either a front side of a substrate wafer or a bottom side of a spring layer;

forming at least one spring-mass connector of a desired height either on the spring layer or on a mass layer; and

joining the substrate wafer, the spring layer and the mass layer such that the spring layer and the substrate wafer are joined through the spring anchor to define a gap therebetween, the mass layer and the spring layer are joined through the spring-mass connector.

2. The method of claim 1 wherein the step of joining the substrate wafer, the spring layer and the mass layer comprises a step using wafer bonding technique.

3. The method of claim 1 wherein the spring-mass connector is horizontally distanced from the spring anchor by a sufficient length to define a cantilever anchored at the spring anchor with an exerting end at the spring-mass connector, the cantilever and the gap enabling a vertical displacement of the spring-mass connector to transport the mass layer substantially vertically with a piston-like motion.

4. The method of claim 1 wherein spring-mass connector is formed on a top side of the spring layer, and the mass layer is connected to the spring-mass connector from the top side of the spring layer opposing the substrate wafer.

5. The method of claim 1 wherein spring-mass connector is formed on the bottom side of the spring layer, and the mass layer is connected to the spring-mass connector from the bottom side of the spring layer.

6. The method of claim 5 wherein the mass layer is disposed in the gap defined by the spring layer and the substrate wafer.

7. The method of claim 1, wherein the step of forming at least one spring anchor comprises:

depositing and patterning a material on the spring layer or the substrate wafer to form the at least one spring anchor.

8. The method of claim 1, wherein the step of forming at least one spring anchor comprises:

growing and patterning an oxide on the spring layer or the substrate wafer to form the at least one spring anchor.

9. The method of claim 1, wherein the step of forming at least one spring anchor comprises:

forming a recess on the spring layer or the substrate wafer; and

growing and patterning an oxide on the spring layer or the substrate wafer to form the at least one spring anchor in the recess, the spring anchor attaching to a bottom of the recess and extending beyond the spring layer or the substrate wafer.

10. The method of claim 1, wherein the step of forming at least one spring-mass connector comprises:

depositing and patterning a material on the mass layer or the spring layer to form the at least one spring-mass connector.

11. The method of claim 1, wherein the step of forming at least one spring-mass connector comprises:

patterning and micromachining the mass layer or the spring layer to form the at least one spring-mass connector on the mass layer.

12. The method of claim 1, wherein the step of forming at least one spring-mass connector comprises:

forming a sacrificial layer on the mass layer or the spring layer, the sacrificial layer defining a negative pattern for the spring-mass connector;

depositing a material over the sacrificial layer and into the negative pattern for the spring-mass connector; and

removing the sacrificial layer to form the spring layer and the spring-mass connector.

13. The method of claim 1 further comprising forming or effectuating a transducing member on the spring layer.

14. The method of claim 13 wherein the transducing member is an electrode.

15. The method of claim 1 wherein the mass layer is disposed between the substrate and the spring layer, the method further comprising forming or effectuating a transducing member on the mass layer.