Electromechanical device treatment with water vapor

• US 7,738,158 B2
• Filed: 06/27/2008
• Issued: 06/15/2010
• Est. Priority Date: 06/29/2007
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Akella, Sriram, Gousev, Evgeni, Khazeni, Kasra, Heald, David, He, Rihui, Natarajan, Bangalore R.
• Primary Examiner(s): Choi; William C
• Application Number:
  US12/163,660
• Publication Number:
  US 20090002804A1
• Time in Patent Office: 718 Days
• Field of Search: 359/199.4, 359/200.8, 359/212.1, 359/224.1, 359/247, 359290-292, 359/295, 359/302
• US Class Current: 359/290
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 3/0005 Anti-stiction coatings
• CPC Class Codes: B81C 1/0092 For avoiding stiction during the manufacturing process of the device, e.g. during wet etching
• CPC Class Codes: B81C 2201/112 Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26

Abstract

Methods, devices, and systems provide MEMS devices exhibiting at least one of reduced stiction, reduced hydrophilicity, or reduced variability of certain electrical characteristics using MEMS devices treated with water vapor. The treatment is believed to form one or more passivated surfaces on the interior and/or exterior of the MEMS devices. Relatively gentle temperature and pressure conditions ensure modification of surface chemistry without excessive water absorption after removal of sacrificial material to release the MEMS devices.

Claims

1. A method for treating an electromechanical device, the method comprising:

providing an electromechanical device comprising a surface that defines at least a portion of a cavity, the surface being exposed by removing a sacrificial material, wherein the surface comprises one of a metal and a dielectric; and

wherein treating the electromechanical device comprises treating the electromechanical device with water vapor at or below ambient pressure such that surface chemistry of the surface is modified to be less susceptible to stiction, relative to the device without water vapor treatment.

2. The method of claim 1, wherein treating the electromechanical device comprises treating at least one of a microelectromechanical systems (MEMS) and a nanoelectromechanical systems (NEMS).

3. The method of claim 1, wherein treating the electromechanical device comprises treating an array comprising a plurality of the electromechanical devices.

4. The method of claim 3, wherein treating the electromechanical device comprises reducing variability, relative to the device without water vapor treatment, of one of:

an actuation voltage among the plurality of the electromechanical devices;

a release voltage among the plurality of the electromechanical devices; and

a hysteresis window among the plurality of the electromechanical devices.

5. The method of claim 1, wherein treating the electromechanical device comprises stabilizing an offset voltage in the electromechanical device.

6. The method of claim 1, wherein treating the electromechanical device with water vapor comprises exposing the electromechanical device to an environment of from about 50% to about 90% relative humidity.

7. The method of claim 1, wherein treating the electromechanical device with water vapor comprises exposing the electromechanical device to an environment of below 85% relative humidity.

8. The method of claim 1, wherein treating the electromechanical device with water vapor comprises treating the electromechanical device with water vapor at a temperature between about 50°

C. to about 120°

C.

9. The method of claim 8, wherein treating the electromechanical device with water vapor comprises treating the electromechanical device with water vapor at a temperature below 100°

C.

10. The method of claim 1, wherein treating the electromechanical device with water vapor comprises exposing the electromechanical device to an environment of 55% to 75% relative humidity at 60°

C. to 80°

C. for 2 to 6 hours.

11. The method of claim 1, wherein treating the electromechanical device with water vapor comprises treating the electromechanical device with pulses of water vapor.

12. The method of claim 1, wherein the sacrificial material is removed by dry etching using an etchant comprising a fluorine-based etchant.

13. The method of claim 12, wherein the etchant is XeF₂.

14. The method of claim 1, wherein the sacrificial material is removed in a chamber that is connected to a load lock.

15. The method of claim 1, further comprising heating the electromechanical device after the sacrificial material is removed and before treating the electromechanical device with water vapor.

16. The method of claim 1, further comprising heat treating the electromechanical device after treating the electromechanical device with water vapor at a temperature of greater than 100°

C.

17. The method of claim 1, further comprising depositing a layer on the surface of the electromechanical device after treating the electromechanical device with water vapor.

18. The method of claim 17, wherein the deposited layer is selected from the group consisting a dielectric layer or a self-assembling monolayer.

19. An apparatus comprising a water-vapor passivated MEMS device, wherein the water-vapor passivated MEMS device comprises:

a first layer comprising a partial reflector;

a reflective layer movable relative to the first layer; and

a cavity, an interior of which is defined by the first layer and the reflective layer, wherein at least a portion of a surface of the cavity is water-vapor passivated after a sacrificial removal process.

20. The apparatus of claim 19, further comprising an upper surface exterior of the cavity, wherein the upper surface exterior of the cavity comprises a water-vapor passivated surface.

21. The apparatus of claim 19, wherein the at least a portion of the surface of the cavity comprises a metal or dielectric surface.

22. The apparatus of claim 19, further comprising:

a display;

a processor that is configured to communicate with said display, said processor being configured to process image data; and

a memory device that is configured to communicate with said processor.

23. The apparatus of claim 22, further comprising a driver circuit configured to send at least one signal to the display.

24. The apparatus of claim 23, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

25. The apparatus of claim 19, further comprising an image source module configured to send said image data to said processor.

26. A method for reducing stiction in a microelectromechanical systems (MEMS) device, the method comprising:

removing a sacrificial material from a MEMS device;

heating the MEMS device after removing the sacrificial material, wherein heating the MEMS device comprises exposing the MEMS device to a maximum temperature lower than approximately 100°

C.; and

exposing and treating the MEMS device with water vapor after heating.

27. The method of claim 26, wherein heating the MEMS device comprises heating the MEMS device to between 50°

C. and 100°

C.

28. The method of claim 26, wherein treating the MEMS device with water vapor comprises exposing a surface to water vapor at a relative humidity of less than 85% relative humidity.

29. The method of claim 26, wherein exposing and treating a MEMS device with water vapor comprises exposing the MEMS device to water vapor at or below ambient pressure.

30. The method of claim 26, wherein exposing and treating the MEMS device with water vapor comprises exposing the MEMS device to water vapor in the same chamber as heating the MEMS device.

31. The method of claim 26, wherein exposing and treating a MEMS device with water vapor comprises exposing the MEMS device to water vapor after the MEMS device has stabilized at a steady state temperature and while maintaining the MEMS device at the steady state temperature.