Micro-electro-mechanical transducer having a surface plate

Inventor: Yongli Huang
Original Assignee: Kolo Technologies, Inc.
Current Assignee: Search USPTO Assignment Database
Primary Examiner: Anh Q Tran
Attorney: Lee & Hayes, PLLC

Patent number: 8018301
Filing date: Jan 31, 2011
Issue date: Sep 13, 2011
Application number: 13/018,162

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 there between 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

What is claimed is:

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.

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