MEMS passivation with phosphonate surfactants

• US 7,410,820 B2
• Filed: 01/05/2005
• Issued: 08/12/2008
• Est. Priority Date: 01/05/2004
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Jacobs, Simon Joshua, Miller, Seth Adrian
• Primary Examiner(s): Nguyen; Tuan H
• Application Number:
  US11/031,655
• Publication Number:
  US 20050147750A1
• Time in Patent Office: 1,315 Days
• Field of Search: 438/51, 438/55, 438/64, 438/106, 438/781
• US Class Current: 438/51
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 3/0005 Anti-stiction coatings
• CPC Class Codes: B81C 2201/112 Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites

Abstract

Phosphonate surfactants are employed to passivate the surfaces of MEMS devices, such as digital micromirror devices. The surfactants are adsorbed from vapor or solution to form self-assembled monolayers at the device surface. The higher binding energy of the phosphonate end groups (as compared to carboxylate surfactants) improves the thermal stability of the resulting layer.

Claims

1. A method for fabricating a MEMS device comprising contacting a surface of said device with a vapor comprising octadecylphosphonic acid or a salt or ester thereof.

2. The method of claim 1, wherein said surface comprises aluminum.

3. The method of claim 1, wherein said MEMS device is a digital micromirror device.

4. The method of claim 1, further comprising, prior to contacting the surface of the device with the vapor, washing the surface with a carbonate or alcohol.

5. The method of claim 4, wherein the carbonate comprises sodium carbonate.

6. The method of claim 1, wherein the vapor comprises an ester of octadecylphosphonic acid and, further comprising, prior to contacting the surface of the device with the vapor, hydroxylating the surface.

7. The method of claim 6, wherein hydroxylating the surface comprises exposing the surface to sulfuric acid, hydrogen peroxide, or a plasma formed from hydrogen, water, ammonia or oxygen.

8. The method of claim 1, wherein the solution comprises an ester of octadecylphosphonic acid and, further comprising, prior to contacting the surface of the device with the solution, hydroxylating the surface.

9. The method of claim 8, wherein hydroxylating the surface comprises exposing the surface to sulfuric acid, hydrogen peroxide, or a plasma formed from hydrogen, water, ammonia or oxygen.

10. A method for fabricating a MEMS device comprising contacting a surface of said device with a solution comprising a solvent and octadecylphosphonic acid or a salt or ester thereof.

11. The method of claim 10, wherein said surface comprises aluminum.

12. The method of claim 10, wherein said MEMS device is a digital micromirror device.

13. The method of claim 10, further comprising, prior to contacting the surface of the device with the solution, washing the surface with a carbonate or alcohol.

14. The method of claim 13, wherein the carbonate comprises sodium carbonate.

15. The method of claim 10, wherein the solvent comprises an alcohol or water.

16. The method of claim 10, wherein the alcohol comprises isopropyl alcohol.

17. A method for fabricating a MEMS device comprising:

washing a surface of the device with a carbonate or alcohol; and

contacting the surface of the device with a solution comprising a solvent and an alkylphosphonic acid or a salt or ester thereof, wherein the alkylphosphonic acid comprises a hydrocarbon straight chain of at least 8-17 carbon atoms.

18. The method of claim 17, wherein the alkylphosphonic acid comprises n-octylphosphonic acid.

19. The method of claim 17, wherein the carbonate comprises sodium carbonate.

20. The method of claim 17, wherein said MEMS device is a digital micromirror device.