MICROELECTROMECHANICAL DEVICE AND METHOD UTILIZING A POROUS SURFACE

• US 20080218843A1
• Filed: 05/13/2008
• Published: 09/11/2008
• Est. Priority Date: 04/19/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Kogut, Lior, Sasagawa, Teruo
• Granted Patent: US 7,944,603 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: B81C 2201/0115 Porous silicon
• 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

A microelectromechanical device (MEMS) utilizing a porous electrode surface for reducing stiction is disclosed. In one embodiment, a microelectromechanical device is an interferometric modulator that includes a transparent electrode having a first surface; and a movable reflective electrode with a second surface facing the first surface. The movable reflective electrode is movable between a relaxed and actuated (collapsed) position. An aluminum layer is provided on either the first or second surface. The aluminum layer is then anodized to provide an aluminum oxide layer which has a porous surface. The porous surface, in the actuated position, decreases contact area between the electrodes, thus reducing stiction.

Claims

1. A method of making an interferometric modulator, comprising:

providing transparent and reflective electrodes facing each other across a collapsible gap;

providing a metallic layer on at least one of facing surfaces; and

anodizing the metallic layer to form an anodized layer.

2. The method of claim 1, wherein the method comprises:

providing the metallic layer over the transparent electrode;

providing a sacrificial layer over the anodized layer; and

forming the reflective electrode over the sacrificial layer.

3. The method of claim 2, further comprising removing the sacrificial layer after forming the reflective electrode.

4. The method of claim 2, wherein the sacrificial layer is formed of a material selected from the group consisting of molybdenum, silicon, and tungsten.

5. The method of claim 1, wherein the method comprises:

providing a sacrificial layer over the transparent electrode;

providing the metallic layer over the sacrificial layer; and

forming a reflective electrode over the anodized layer.

6. The method of claim 5, further comprising removing the sacrificial layer after forming the reflective electrode.

7. The method of claim 1, wherein the metallic layer comprises aluminum.

8. The method of claim 1, wherein anodizing the metallic layer comprises using an acid selected from the group consisting of sulfuric, phosphoric, oxalic, chromic, and citric acid.

9. The method of claim 1, wherein anodizing the metallic layer comprises only partially anodizing the metallic layer.

10. The method of claim 1, wherein forming the transparent electrode further comprises providing a dielectric layer over a conductive layer.

11. The method of claim 10, wherein the dielectric layer comprises at least one selected from the group consisting of silicon dioxide and aluminum oxide.

12. The method of claim 10, wherein providing the dielectric layer comprises providing a silicon dioxide layer over the conductive layer, and providing an aluminum oxide layer over the silicon dioxide layer.

20. An interferometric modulator made by the method of claim 1.

13. A method of making an electrostatic microelectromechanical systems device, comprising:

providing transparent and reflective electrodes facing each other across a cavity; and

providing a porous layer on at least one of the electrodes, the porous layer facing the other of the electrodes.

14. A method of making a microelectromechanical systems device, comprising:

forming a lower electrode;

forming a sacrificial layer over the lower electrode;

forming an upper electrode;

forming a porous layer between forming the lower electrode and forming the upper electrode.

15. The method of claim 14, wherein forming the porous layer comprises forming the porous layer prior to forming the sacrificial layer.

16. The method of claim 14, wherein forming the porous layer comprises forming the porous layer after forming the sacrificial layer.

17. The method of claim 14, wherein forming the porous layer comprises forming a porous layer prior to forming the sacrificial layer and another porous layer after forming the sacrificial layer.

18. The method of claim 14, further comprising removing the sacrificial layer.

19. The method of claim 18, wherein the porous layer is not removed at the step of removing the sacrificial layer.