Passivation for micromechanical devices

• US 6,259,551 B1
• Filed: 09/27/1999
• Issued: 07/10/2001
• Est. Priority Date: 09/30/1998
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Jacobs, Simon Joshua
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): THOMPSON, TIMOTHY J
• Application Number:
  US09/408,094
• Time in Patent Office: 652 Days
• Field of Search: 359/298, 359/291, 359/290, 359/295, 359/296, 257/682, 427/162, 427/255.6
• US Class Current: 359/298
• CPC Class Codes: B81B 1/00 Devices without movable or flexible elements, e.g. microcapillary devices
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C23C 14/06 characterised by the coating material C23C14/0021 , C23C14/04 take precedence
• CPC Class Codes: G02B 1/10 Optical coatings produced by application to, or surface treatment of, optical elements G02B1/08 takes precedence
• 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

Abstract

A non-volatile passivation coating for micromechanical devices. The device has at least one surface (10) that contacts other surfaces and requires passivation. The passivation is provided by a monolayer of molecules (16) that has cross links (18) between the monolayers, or is of an highly stable material. The monolayer is applied by vacuum vapor coating, melt coating or coating from solution. The non-volatility of the monolayer eliminates the need for a hermetic package.

Claims

1. A micromechanical device, comprising:

a. a structure with at least one moving element that comes into contact with other surfaces;

b. a passivation layer on said moving element, said passivation layer comprised of materials with cross-linking capabilities; and

c. a package containing said structure.

2. The device of claim 1 wherein said structure is a digital micromirror device.

3. A micromechanical device, comprising:

a. a structure with at least one moving element that comes into contact with other surfaces;

b. a passivation layer on said moving element, said passivation layer comprised of materials with cross-linking capabilities selected from the group consisting of;

vinyl, alkoxylsilyl, ethynyl, diethynyl, and amides; and

c. a package containing said structure.

14. The device of claim 3 wherein said structure is a digital micromirror device.

4. A micromechanical device, comprising:

a. a structure with at least one moving element that comes into contact with other surfaces;

b. a passivation layer on said moving element, wherein said passivation layer is comprised of a material having the formula CF₃(CF₂)_n(CH₂)_mCOOH, wherein n is greater than or equal to 7 and m is greater than or equal to 1; and

c. a package containing said structure.

15. The device of claim 4 wherein said structure is a digital micromirror device.

5. A micromechanical device, comprising:

a. a structure with at least one moving element that comes into contact with other surfaces;

b. a passivation layer on said moving element, wherein said passivation layer is comprised of a material having the chemical formula of CF₃(CF₂)_n(CH₂)_mSi(OR)₃, wherein n and m are greater than or equal to zero and less than or equal to ten, and R is a straight-chain alkyl; and

c. a package containing said structure.

16. The device of claim 5 wherein said structure is a digital micromirror device.

6. A micromechanical device, comprising:

a. a structure with at least one moving element that comes into contact with other surfaces;

b. a passivation layer on said moving element, wherein said passivation layer is comprised of a material having the chemical formula of CF₃(CF₂)_m-linker-(CH₂)_nCOOH, wherein said linker is a non-branched organic chain; and

c. a package containing said structure.

17. The device of claim 6 wherein said structure is a digital micromirror device.

7. A method for packaging a micromechanical device, comprising the steps of:

a. providing a micromechanical device requiring passivation;

b. cleaning and reactivating at least one surface of said device for passivation;

c. applying said passivant to said device as a monolayer film;

d. aging said film to facilitate crosslinking between molecules of said monolayer; and

e. sealing said package.

8. The method of claim 7 wherein said providing a micromechanical device step further comprises the steps of partially sawing a wafer upon which are digital micromirror devices;

breaking said wafer into die;

attaching said die; and

bonding said die.

9. The method of claim 7 wherein said cleaning step is accomplished with an oxygen plasma clean.

10. The method of claim 7 wherein said application step comprises melt coating.

11. The method of claim 7 wherein said application step comprises vacuum vapor coating.

12. The method of claim 7 wherein said application step comprises coating from solution with a solvent.

13. The method of claim 7 wherein said sealing step produces a non-hermetic seal.