Protection layers in micromirror array devices

• US 7,459,402 B2
• Filed: 05/24/2005
• Issued: 12/02/2008
• Est. Priority Date: 02/12/2003
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Patel, Satyadev, Doan, Jonathan, Heureux, Peter
• Primary Examiner(s): CHEN, KIN CHAN
• Application Number:
  US11/135,699
• Publication Number:
  US 20050206993A1
• Time in Patent Office: 1,288 Days
• Field of Search: 438/700, 438/706, 438/712, 438/719, 438/720, 438/723, 438/724, 438/725
• US Class Current: 438/723
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

To protect the structural layers from being eroded in the etching process, a protection layer is deposited on the exposed structural layers of the micromirror. The protection layer is deposited before etching and removed after etching.

Claims

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

depositing first and second sacrificial layers on a substrate;

forming a reflective mirror plate on one of the first or second sacrificial layers;

forming a deformable hinge on the other sacrificial layer;

depositing a protection layer on the formed deformable hinge;

removing the sacrificial layer and protection layer so as to free the mirror plate.

2. The method of claim 1, wherein the protection layer is more resistant to a first etching than a structural layer of the device;

and less resistant to a second etching than the structural layer; and

wherein the structural layer is a layer that remains after the sacrificial layer is removed.

3. The method of claim 2, wherein the first etching is an etching process that Patterns a structural layer of the device.

4. The method of claim 2, wherein the second etching is an etching process that thoroughly removes substantially all sacrificial layers.

5. The method of claim 4, wherein the first etching is a breakthrough etching in removing the first and second sacrificial layers.

6. The method of claim 4, wherein the first etching is an etching process that patterns a structural layer of the device.

7. The method of claim 1, wherein the protection layer comprises W.

8. The method of claim 1, wherein the protection layer comprises WNi_x.

9. The method of claim 1, wherein the protection layer comprises amorphous silicon.

10. The method of claim 9, wherein the hinge comprises SiNx.

11. The method of claim 9, wherein the hinge comprises TiNx.

12. The method of claim 1, wherein the step of removing the sacrificial and protection layers further comprises:

removing at least a first portion of the sacrificial materials using a plasma etch, while leaving a second portion of the sacrificial materials; and

removing the second portion of the sacrificial materials and protection layer using a spontaneous vapor phase etchant.

13. The method of claim 12, wherein at least a portion of the protection layer remains after the plasma etch.

14. The method of claim 12, wherein the spontaneous vapor phase chemical etchant comprises an interhalogen.

15. The method of claim 14, wherein the spontaneous vapor phase chemical etchant comprises a noble gas halide.

16. The method of claim 15, wherein the noble gas halide is xenon difluoride.

17. The method of claim 15, wherein the etchant comprises a diluent gas.

18. The method of claim 1, wherein the substrate is transmissive to visible light.

19. The method of claim 1, wherein the substrate is a standard semiconductor substrate on which an integrated circuit can be fabricated.

20. The method of claim 1, wherein the first sacrificial layer is deposited on the substrate;

wherein the mirror plate is formed on the first sacrificial layer;

wherein the second sacrificial layer is deposited and patterned on the first sacrificial layer and the formed mirror plate; and

wherein the deformable hinge is formed on the second sacrificial layer.

21. The method of claim 2, wherein the first sacrificial layer is deposited on the substrate that is a semiconductor substrate;

wherein the deformable hinge is formed on the first sacrificial layer;

wherein the second sacrificial layer is deposited on the first sacrificial layer and the deformable hinge; and

wherein the mirror plate is formed on the second sacrificial layer.

22. The method of claim 2, wherein the step of forming the mirror plate further comprises:

depositing first and second mirror plate layers, wherein the first layer comprises a visible light reflective layer; and

wherein the second mirror plate layer comprises a mechanical enhancing layer for improving a mechanical property of the mirror plate.

23. The method of claim 22, wherein the first mirror plate layer is electrically conductive.

24. The method of claim 23, wherein the second mirror plate layer is electrically insulating.

25. A method of fabricating a hinged MEMS device, comprising:

depositing a sacrificial layer on a substrate;

depositing and patterning a flexible hinge structure and a rigid movable member after depositing the sacrificial layer;

depositing a protection layer on the flexible hinge;

removing the sacrificial layer and the protection layer so as to release the MEMS device, wherein the depositing of a sacrificial layer on a substrate comprises depositing a first and second sacrificial layer on the substrate, wherein the depositing and patterning of the hinge and movable member comprise, after depositing the first sacrificial layer, depositing and patterning the movable member, followed by depositing the second sacrificial layer, followed by depositing and patterning the hinge structure.

26. A method of making a MEMS device, comprising:

on an array of movable plates connected to a substrate, depositing a sacrificial layer;

on the sacrificial layer, depositing a hinge layer and patterning the hinge layer into an array of hinges;

on the array of hinges, depositing a protection layer; and

removing the sacrificial layer and the protection layer.