Electrically conductive protection layer and a microelectromechanical device using the same

• US 7,997,744 B2
• Filed: 03/12/2008
• Issued: 08/16/2011
• Est. Priority Date: 03/12/2008
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Rothenbury, David
• Primary Examiner(s): Cherry; Euncha P
• Application Number:
  US12/046,588
• Publication Number:
  US 20090231672A1
• Time in Patent Office: 1,252 Days
• Field of Search: 359/290, 359/291, 359/295, 359/302, 359/849
• US Class Current: 359/849
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A deformable hinge for use in microelectromechanical devices comprises a protection layer that is electrically conductive. The protection layer is on top of another hinge layer; and is more resistive than the hinge layer to the etchant used in during patterning and/or release processes during fabrication of the microelectromechanical device. As a result, the hinge layer can be protected from being damaged during the fabrication process.

Claims

1. A method of making a micromirror device, comprising:

providing a substrate having an electrode formed thereon;

forming a sacrificial layer comprising a sacrificial material on the substrate;

forming a deformable hinge on the sacrificial layer;

forming a protective layer on a surface of the deformable hinge, wherein the protective layer is electrically conductive;

forming a second sacrificial layer on the deformable hinge;

forming a mirror plate on the second sacrificial layer;

performing an etching process using an etchant to remove the first and the second sacrificial layers, wherein the protective layer is more resistant to the etching process than the deformable hinge.

2. The method of claim 1, wherein the etchant is a fluorine chemical compound or a chlorine chemical compound.

3. The method of claim 2, wherein the protective layer comprises TiN_x;

wherein the deformable hinge comprises Ti_xAl_y.

4. The method of claim 2, further comprising:

before forming the deformable hinge on the first sacrificial layer, forming another protective layer on the first sacrificial layer; and

wherein the deformable hinge is formed on said another protective layer.

5. The method of claim 4, further comprising:

depositing said another protective layer;

depositing a layer of said deformable hinge;

patterning said layer of the deformable hinge by an etching process using an etchant, wherein said etchant and the etching process is substantially incapable of etching said another protective layer.

6. The method of claim 5, wherein said another protective layer is patterned prior to or after the step of patterning said layer of the deformable hinge.

7. The method of claim 1, wherein the step of forming a protective layer on a surface of the deformable hinge is performed after the step of performing an etching process using an etchant to remove the first and the second sacrificial layers.

8. The method of claim 7, further comprising:

forming another protective layer on a surface of the released deformable hinge by sputtering.

9. The method of claim 8, wherein said another protective layer comprises TiN_x;

and wherein the deformable hinge comprises Ti_xAl_y.

10. The method of claim 1, wherein the deformable hinge is a torsion hinge that is capable of deforming after the first and second sacrificial layers being removed.

11. The method of 10, wherein the protective layer is formed on a top surface of the deformable hinge;

and said another protective layer is formed on a bottom surface of the deformable hinge; and

wherein the protective layer is electrically connected to the mirror plate; and

said another protective layer is electrically connected to the electrode on the substrate.

12. A micromirror device, comprising:

a substrate having an electrode and a hinge connection pad formed thereon;

a deformable hinge held above the substrate, comprising;

an intermediate hinge layer laminated between a top and a bottom hinge layer, wherein the top and the bottom hinge layers comprise an electrically conductive material that is different from the material of the intermediate hinge layer;

a mirror plate attached to the deformable hinge such that the mirror plate is capable of moving above the substrate; and

wherein the mirror plate is electrically connected to the top hinge layer through a mirror post; and

the bottom hinge layer is electrically connected to the hinge connection pad.

13. The device of claim 12, wherein the top and the bottom hinge layers are TiN_x layers.

14. The device of claim 13, wherein the intermediate hinge layer is a TiAl_x layer.

15. The device of claim 13, wherein the top and bottom hinge layers each are more resistant to an etching process that is applied for patterning the intermediate hinge layer.

16. The device of claim 15, wherein the top and the bottom hinge layers each have an etching rate that is 1/20th or less than the etching rate of the intermediate hinge layer to the etching process.

17. A method of making a micromirror device, the method comprising:

providing a substrate having formed thereon an electrical circuit;

depositing and patterning a first sacrificial layer on the substrate;

forming a deformable hinge on the first sacrificial layer, comprising;

depositing a bottom hinge layer on the first sacrificial layer;

depositing an intermediate hinge layer on the bottom hinge layer;

depositing a top hinge layer on the intermediate hinge layer;

patterning the bottom, the intermediate, and the top hinge layers, together or separately, so as to form the deformable hinge;

depositing a second sacrificial layer on the patterned deformable hinge;

forming a mirror plate on the second sacrificial layer; and

removing the first and the second sacrificial layers so as to release the micromirror device.

18. The method of claim 17, wherein the top, the intermediate, and the bottom hinge layers are laminated such that the top and the bottom surfaces of the intermediate hinge layer are substantially fully covered by the top and the bottom hinge layers.

19. The method of claim 18, wherein the top or the bottom hinge layers are deposited by an in-situ deposition process.

20. The method of claim 19, wherein the top and the bottom hinge layers are electrically conductive.

21. The method of claim 20, wherein the intermediate hinge layer is electrically conductive and comprises a material that is different from a material of the top and the bottom hinge layers.

22. The method of claim 21, wherein the intermediate hinge comprises a material that is more resistant to an etching process applied for patterning the intermediate layer than the top and the bottom hinge layers.

23. The method of claim 22, wherein the top and the bottom layers each comprise a TiN_x material;

and the intermediate hinge layer comprises a TiAl_x layer.

24. The method of claim 18, wherein the step of providing the substrate further comprises:

forming an electrode and a hinge connection pad on the substrate.