Methods of applying coatings to micro electromechanical devices using a carbon dioxide carrier solvent

• US 20030064149A1
• Filed: 09/12/2002
• Published: 04/03/2003
• Est. Priority Date: 09/28/2001
• Status: Abandoned Application

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Miller, Seth A.
• Application Number:
  US10/241,999
• Publication Number:
  US 20030064149A1
• Time in Patent Office: Days
• US Class Current: 427/126.3
• CPC Class Codes: B05D 1/025 using gas close to its critical state
• CPC Class Codes: B05D 2401/90 at least one component of the composition being in supercritical state or close to supercritical state
• CPC Class Codes: B81B 3/0005 Anti-stiction coatings
• CPC Class Codes: B81C 1/0096 For avoiding stiction when the device is in use, i.e. after manufacture has been completed
• CPC Class Codes: B81C 2201/112 Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
• CPC Class Codes: B81C 2201/117 Using supercritical fluid, e.g. carbon dioxide, for removing sacrificial layers
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A method of coating one or more surfaces of a micromechanical device. The coating is applied as a material dissolved in CO2. The CO2 is used a carrier solvent, with the coating being applied as a spray or in liquid form, to form a film on the surface. The CO2 may be used in supercritical form to dissolve the material.

Claims

1. A method of coating at least one surface of a micro-mechanical device, comprising the steps of:

dissolving a coating material in CO2; and

depositing the dissolved material on at least one exposed surface of the device.

2. The method of claim 1, wherein the CO2 is in liquid form.

3. The method of claim 1, wherein the CO2 is in a supercritical state during the dissolving step only.

4. The method of claim 1, wherein the CO2 is in a supercritical state during the dissolving step and the depositing step.

5. The method of claim 1, wherein the depositing step is performed by vapor deposition, thermal evaporation, nebulization, dipping, or spinning.

6. The method of claim 1, wherein the depositing step is performed by spraying the dissolved material

7. The method of claim 5, wherein the spraying is performed with a nebulizer.

8. The method of claim 1, wherein the micro-mechanical device is of the type having a first element selectively movable relative to a second element, portions of the elements contacting in one position of the first element, and wherein the depositing step is performed so as to coat at least one of the elements.

9. The method of claim 1, wherein at least one of the surfaces includes aluminum oxide.

10. The method of claim 1, wherein the depositing step results in a film of about 5 angstroms to about 100 angstroms thick.

11. The method of claim 1, wherein the coating material is primarily a fluorocarbon material.

12. The method of claim 1, wherein the coating material is primarily a perfluoropolyether (PFPE).

13. The method of claim 12, wherein the perfluoropolyether (PFPE) is Z-type, Y-type, Krytox or Demnum.

14. The method of claim 12, wherein the perfluoropolyether (PFPE) has incorporated thereinto as functional chemical groups carboxylic, hydroxyl, ether or phenolic groups.

15. The method of claim 1 wherein the coating material is acetal-deficient, acetal-free or acetal-rich perfluoropolyether (PFPE) or a mixture of two or more thereof.

16. The method of claim 1, wherein the coating material is a perfluorodecanoic acid (PFDA).

17. A MEMS device operable for modulating light having lubricated moving parts, comprising:

a silicon substrate having CMOS memory circuitry;

address electrodes and landing pads fabricated over the silicon substrate;

a hinge assembly fabricated over the silicon substrate;

a mirror attached to the hinge assembly;

wherein the hinges are operable to rotate in response to electrostatic forces resulting from electrical activation of the address electrodes; and

wherein the surfaces of at least the landing pads are lubricated with a material dissolved in and carried by CO2.

18. The device of claim 17, wherein the hinges are torsion hinges on the same level as the mirror.

19. The device of claim 17, wherein the hinge assembly is located at a level lower than the mirror.

20. A back-end process for fabricating MEMS devices with lubricated micro-machined parts, comprising the steps of:

fabricating a wafer of the MEMS devices;

partially sawing the wafer;

testing the wafer;

completing sawing of the wafer, thereby separating the wafer into individual devices;

packaging the devices; and

applying a lubricating material to exposed surfaces of the devices by applying a nebulized solution to the devices, the solution being comprised of at least one coating material dissolved in and carried by CO2.