Stressed material and shape memory material MEMS devices and methods for manufacturing

• US 7,372,348 B2
• Filed: 08/20/2004
• Issued: 05/13/2008
• Est. Priority Date: 08/20/2004
• Status: Expired due to Fees

• Current Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Xu, Baomin, Young, Michael Yu Tak, Chow, Eugene Michael, Fork, David Kirtland
• Primary Examiner(s): ROJAS, BERNARD
• Application Number:
  US10/923,277
• Publication Number:
  US 20060038643A1
• Time in Patent Office: 1,362 Days
• Field of Search: 335/78, 200/181
• US Class Current: 335/78
• CPC Class Codes: F03G 7/065 using a shape memory element
• CPC Class Codes: F04B 17/003 driven by piezoelectric means F04B43/046 and F04B43/095 take precedence
• CPC Class Codes: F05C 2201/0412 Titanium
• CPC Class Codes: F05C 2203/0813 Carbides
• CPC Class Codes: F05C 2251/00 Material properties
• CPC Class Codes: F05C 2251/08 Shape memory
• CPC Class Codes: G11C 23/00 Digital stores characterised by movement of mechanical parts to effect storage, e.g. using balls; Storage elements therefor
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end

Abstract

Disclosed is a MEMS device which comprises at least one shape memory material such as a shape memory alloy (SMA) layer and at least one stressed material layer. Examples of such MEMS devices include an actuator, a micropump, a microvalve, or a non-destructive fuse-type connection probe. The device exhibits a variety of improved properties, for example, large deformation ability and high energy density. Also provided is a method of easily fabricating the MEMS device in the form of a cantilever-type or diaphragm-type structure.

Claims

1. A device comprising:

at least one thin film layer of a shape memory material or materials; and

at least one thin film layer of a stressed and conductive metal material or metal alloy material adjacent to the at least one thin film layer of the shape memory material;

the thin film layer of the stressed metal material or metal alloy material possessing an inherent stress or stress gradient imparted to that metal material or metal alloy material layer during its deposition, such that as a result of the inherent stress or stress gradient in the thin film layer or layers of the stressed metal material or metal alloy material, the device is biased to an initial deformation state, wherein the inherent stress is different from an inherent stress in a normally manufactured metal or metal alloy.

2. The device of claim 1 wherein the layer of the shape memory material is immediately adjacent to the layer of the stressed material.

3. The device of claim 1 wherein the layer of stressed material has a uniform composition across its thickness.

4. The device of claim 1, wherein the shape memory material is a shape memory alloy (SMA) selected from the group consisting of NiAl, TiNi, TiNiHf, TiNiCu, TiNiNb, TiNiPd, TiNiCo, TiPdNi, AgCd, AuCd, CuZn, CuZnGa, CuZnSi, CuZnSn, CuZnAl, CuAlNi, CuSn, CuAuZn, InTl, InCd, MnCd, and combinations thereof.

5. The device of claim 1, wherein the shape memory material is selected from the group consisting of polymer materials, ceramic materials, and combinations thereof.

6. The device of claim 1, wherein the stressed metal or alloy material is selected from the group consisting of , molybdenum (Mo), “

molybdenum-chrome”

alloy (MoCr), tungsten (W), titanium-tungsten alloy (TiW), chromium (Cr), nickel (Ni), nickel-zirconium alloy (NiZr), and combinations thereof.

7. The device of claim 1, wherein the stress in the stressed material is greater than 100 MPa.

8. The device of claim 1, wherein the stress gradient in the stressed material is greater than 200 MPa/μ

m.

9. The device of claim 1, wherein the device is in the form of a cantilever, with one or both ends clamped or secured to a substrate.

10. The device of claim 1, wherein the shape memory material has a martensite-austenite phase transition temperature of from about −

200°

C. to about 110°

C.

11. The device of claim 1, wherein the device is selected from the group consisting of an actuator, a microswitch, a microvalve, a micropump, and a non-destructive fuse-type connection probe.

12. A reversible and selectively deformable MEMS device comprising:

a released assembly including (i) a single layer of a stressed and conductive metal material or alloy material having a uniform composition across its thickness and having an inherent mechanical stress or stress gradient, the stress being defined at a pre-release state of the assembly, and (ii) at least one other layer proximate to the layer of stressed material, the other layer serving to apply a mechanical load upon the layer of stressed material, wherein the inherent stress is different from an inherent stress in a normally manufactured metal or metal alloy;

wherein the inherent mechanical stress or stress gradient in the layer of stressed material causes the assembly to assume a post-release state, and upon selectively changing the physical properties of the other layer, the assembly is reversibly and selectively deformed to another state different than the post-release state.

13. The device of claim 12, wherein the stress in the stressed material is greater than 100 MPa.

14. The device of claim 12, wherein the stress gradient in the stressed material is greater than 200 MPa/μ

m.

15. A selectively deformable MEMS curved device comprising:

a single shape memory alloy layer alone, wherein the shape memory alloy itself exhibits an inherent stress gradient in the thickness direction of the film, the stress gradient in the shape memory alloy layer causes the device to assume an initial deformation state, and changing the mechanical properties or stress gradient of the shape memory alloy layer by changing the temperature causes the device to assume another deformation state different than the initial deformation state.

16. The device of claim 15, wherein the stress gradient in the stressed material is greater than 200 MPa/μ

m.

17. A device comprising:

at least one layer of a shape memory material or materials; and

a single layer of a stressed and conductive metal or alloy material adjacent to the layer or layers of the shape memory material;

the layer having a uniform composition across its thickness, and possessing an inherent stress or stress gradient imparted to that layer during its formation, such that as a result of the inherent stress or stress gradient in the layer of the stressed metal or alloy material, the device is biased to an initial deformation state, wherein be inherent stress is different from an inherent stress in a normally manufactured metal or metal alloy.

18. The device of claim 17 wherein the layer of the shape memory material is immediately adjacent to the layer of the stressed material.

19. The device of claim 17, wherein the shape memory material is a shape memory alloy (SMA) selected from the group consisting of NiAl, TiNi, TiNiHf, TiNiCu, TiNiNb, TiNiPd, TiNiCo, TiPdNi, AgCd, AuCd, CuZn, CuZnGa, CuZnSi, CuZnSn, CuZnAl, CuAlNi, CuSn, CuAuZn, InTl, InCd, MnCd, and combinations thereof.

20. The device of claim 17, wherein the stressed material is a metal or alloy selected from the group consisting of, molybdenum (Mo), “

molybdenum-chrome”

alloy (MoCr), tungsten (W), titanium-tungsten alloy (TiW), chromium (Cr), nickel (Ni), nickel-zirconium alloy (NiZr), and combinations thereof.

21. The device of claim 17, wherein the stress in the stressed material is greater than 100 MPa.

22. The device of claim 17, wherein the stress gradient in the stressed material is greater than 200 MPa/μ

m.