# US 7,410,820 B2 · MEMS passivation with phosphonate surfactants

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- Number: US 7,410,820 B2
- Document ID: US7410820B2
- Status: Granted
- Kind: B2
- Application number: 11/031,655
- Filed: 2005-01-05
- Published: 2005-07-07
- Granted: 2008-08-12
- Earliest claimed: 2004-01-05
- Assignees: Texas Instruments Incorporated
- Inventors: Simon Joshua Jacobs; Seth Adrian Miller
- Web page: https://patentgrep.com/patent/US7410820B2

## CPC

- B81B 3/0005: {Anti-stiction coatings}
- B81B 2201/042: Micromirrors, not used as optical switches
- B81C 2201/112: Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00)
- B81C: PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS (making microcapsules or microballoons B01J13/02; processes or apparatus specially adapted for the manufacture or treatment of piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/01)
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES

## 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

### Claim 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.

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

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.

### Claim 5 (depends on 4)

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

### Claim 6 (depends on 1)

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.

### Claim 7 (depends on 6)

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.

### Claim 8 (depends on 1)

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.

### Claim 9 (depends on 8)

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.

### Claim 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.

### Claim 11 (depends on 10)

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

### Claim 12 (depends on 10)

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

### Claim 13 (depends on 10)

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.

### Claim 14 (depends on 13)

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

### Claim 15 (depends on 10)

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

### Claim 16 (depends on 10)

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

### Claim 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.

### Claim 18 (depends on 17)

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

### Claim 19 (depends on 17)

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

### Claim 20 (depends on 17)

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