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

• US 20060038643A1
• Filed: 08/20/2004
• Published: 02/23/2006
• Est. Priority Date: 08/20/2004
• Status: Active Grant

• 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
• Granted Patent: US 7,372,348 B2
• Time in Patent Office: Days
• 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 layer of a shape memory material or materials; and

at least one layer of a stressed material or materials adjacent to the layer or layers of the shape memory material;

the layer or layers of the stressed material possessing an inherent stress or stress gradient imparted to that layer or layers during its or their formation, such that as a result of the inherent stress or stress gradient in the layer or layers of the stressed material or materials, the device is biased to an initial deformation state.

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 material is selected from the group consisting of metal, alloy, oxide, nitride, semiconductor, silicon (Si), carbide, diamond, ceramics, polymer, and combinations thereof.

7. The device of claim 1, wherein the stressed material is a metal or alloy selected from the group consisting of Ni, Mo, “

molybdenum-chrome”

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

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

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

m.

10. 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.

11. The device of claim 1, wherein the device is in the form of a diaphragm.

12. 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.

13. The device of claim 1 further comprising electrical contacts for providing electrical communication to at least one of the layer of the shape memory material and the layer of the stressed material, whereby upon passing an electrical current through the electrical contacts and layer(s) in communication therewith, heat is generated.

14. The device of claim 1, further comprising a resistive heating element.

15. The device of claim 1, further comprising one or more layers of a metal which has a thermal expansion coefficient that is significantly different from those of the shape memory material and the stressed material.

16. The device of claim 1, further comprising a thin film sensor layer to detect the deformation of the device, the thin film layer having dimensions equal or smaller than corresponding dimensions of at least one of the shape memory layer and the stressed material layer, and the thin film layer including a material selected from the group consisting of a piezoelectric material, a piezoresistive material, and combinations thereof.

17. 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.

18. The device of claim 1, wherein the device comprises two or more layers of a stressed material or materials.

19. A reversible and selectively deformable MEMS device comprising:

a released assembly including (i) at least one layer of a stressed material 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 mechanical stress 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.

20. The device of claim 19, wherein the other layer is a piezoelectric material having physical properties that can be changed by applying an electric field.

21. The device of claim 19, wherein the other layer is an electrostrictive material having physical properties that can be changed by applying an electric field.

22. The device of claim 19, wherein the other layer is a magnetostrictive material having physical properties that can be changed by applying a magnetic field.

23. A selectively deformable MEMS curved device comprising:

at least one shape memory alloy layer, wherein the shape memory alloy exhibits an inherent stress gradient, the stress gradient in the at least one shape memory alloy layer causes the device to assume an initial deformation state, and changing the mechanical properties or stress gradient of the at least one shape memory alloy layer by changing the temperature causes the device to assume another deformation state different than the initial deformation state.

24. The MEMS device of claim 23, wherein the device comprises a single shape memory alloy layer.

25. The MEMS device of claim 23, wherein the device comprises two or more shape memory alloy layers.

26. A method of making a device including (i) at least one shape memory alloy (SMA) layer and (ii) at least one stressed material layer, the device having a cantilever structure, the method comprising:

providing a substrate,

depositing a sacrificial layer on the substrate;

depositing and annealing a SMA film;

depositing a stressed material film, in which the deposition parameters of the stressed material are controlled to induce stress or produce a stress gradient in the stressed material film; and

at least partially removing the sacrificial layer, to thereby release the SMA film and stressed material film from the substrate and produce a cantilevered layered device.

27. The method of claim 26, in which the SMA film is deposited by a process selected from the group consisting of evaporation, vapor deposition, and sputtering methods.

28. The method of claim 26, further including annealing the SMA film at a temperature within the range of from about 400°

C. to about 800°

C.

29. The method of claim 26, further including a step of annealing the SMA film at a temperature less than about 200°

C.

30. The method of claim 26, further including depositing a dielectric layer on the SMA film.

31. The method of claim 26 wherein the SMA film is deposited on the sacrificial layer, and the stressed material film is deposited on the SMA film.

32. The method of claim 26 wherein the stressed material film is deposited on the sacrificial layer, and the SMA film is deposited on the stressed material film.

33. A method of making a device including (i) at least one shape memory alloy (SMA) layer and (ii) at least one stressed material layer, the device having a diaphragm structure, the method comprising:

providing a substrate;

depositing a SMA film;

depositing a stressed material film and controlling the deposition parameters to induce stress or stress gradient in the stressed material film; and

patterning the substrate material to form a cavity.

34. The method of claim 33, in which the SMA film is deposited by a method selected from the group consisting of evaporation, vapor deposition, and sputtering.

35. The method of claim 33, further including a step of annealing the SMA film at 400 to 800°

C.

36. The method of claim 33, further including annealing the SMA film at a temperature less than or equal to 200°

C.

37. The method of claim 33, further including depositing a dielectric layer on the SMA film.

38. The method of claim 33 wherein the SMA film is deposited on the substrate and the stressed material film is deposited on the SMA film.

39. The method of claim 33 wherein the stressed material film is deposited on the substrate and the SMA film is deposited on the stressed material film.

40. A method of producing a device including (i) at least one shape memory alloy (SMA) layer and (ii) at least one stressed material layer, the method comprising:

providing a first substrate;

depositing a sacrificial layer on the substrate;

depositing and annealing a SMA film;

depositing a stressed material film, wherein the deposition parameters are controlled to induce stress or produce a stress gradient in the stressed material film;

affixing a target substrate to the stressed material film; and

removing the sacrificial layer and the first substrate.

41. The method of claim 40 wherein the target substrate includes a second sacrificial layer and the step of affixing is performed by affixing the second sacrificial layer to the stressed material film;

the method further comprising;

removing the second sacrificial layer to thereby release the device in a cantilevered form.

42. The method of claim 40 further comprising:

selectively removing a portion of the target substrate to thereby produce the device in a diaphragm form.

43. The method of claim 40 wherein the SMA film is deposited on the sacrificial layer and the stressed material film is deposited on the SMA film.

44. The method of claim 40 wherein the stressed material film is deposited on the sacrificial layer and the SMA film is deposited on the stressed material film.