Electrostatic efficiency of micromechanical devices

• US 6,552,840 B2
• Filed: 11/30/2000
• Issued: 04/22/2003
• Est. Priority Date: 12/03/1999
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Knipe, Richard L.
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): TRA, TUYEN Q
• Application Number:
  US09/726,861
• Publication Number:
  US 20020093721A1
• Time in Patent Office: 873 Days
• Field of Search: 359/290, 359/291, 359/292, 359/214, 359/213, 359/221, 359/224, 359/295, 359/223, 359/226, 359/298
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

An improved micromechanical device, particularly a micromirror device having improved electrostatic efficiency. A deflectable member comprised of a mirror 302 and an active hinge yoke 306 is suspended address 308 and landing electrodes 312 on a substrate 310 and above upper address electrodes supported above the substrate 310. The deflectable member is operable to rotate about a torsion hinge axis in response to an electrostatic force between the address electrodes and the deflectable member. The upper address electrodes have a stair stepped shape to narrow a gap between the deflectable member and the upper address electeodes. The gap is narrower near the axis of rotation 810 compared to away from the axis. The stair stepped shape is achieved by embedding a portion of an oxide layer 804 between a thin metal layer 806 making up the upper address electrodes 806, the active hinge yoke 306, and the torsion hinges, and a thick metal layer 808 making up the upper address electrodes 806 and the active hinge yoke 306.

Claims

1. A micromechanical device having improved electrostatic efficiency, said device comprising:

a first member forming one half of an air-gap capacitor; and

a second member forming one half of an air gap capacitor, said second member spaced apart from said first member by an air gap, said first member operable to deflect between an undeflected position and at least one deflected position, said second member having a beveled surface such that said air gap is smaller in a first region than in a second region when said second member is in said undeflected sate.

2. A micromirror device comprising:

a substrate;

an address electrode supported by said substrate said address electrode having a beveled surface;

a deflectable member supported by said substrate and spaced apart from said address electrode by a gap, said deflectable member operable to rotate around a hinge axis between an undeflected position and at least one deflected position, said address electrode and said deflectable member such that when said deflectable member is in said undeflected position said gap is narrower over a first region and wider over a second region farther from said hinge axis than said first region.

3. The micromirror device of claim 2, wherein said address electrode is an upper address electrode.

4. The micromirror device of claim 2, wherein said address electrode is a lower address electrode.

5. A micromirror device comprising:

a substrate;

an address electrode supported by said substrate said address electrode having a stair stepped surface;

a deflectable member supported by said substrate and spaced apart from said address electrode by a gap, said deflectable member operable to rotate around a hinge axis between an undeflected position and at least one deflected position, said address electrode and said deflectable member such that when said deflectable member is in said undeflected position said gap is narrower over a first region and wider over a second region farther from said hinge axis than said first region.

6. The micromirror device of claim 5, said stair stepped surface formed by encapsulating an oxide layer between two metal layers.

7. The micromirror device of claim 5, wherein said address electrode is an upper address electrode.

8. The micromirror device of claim 5, wherein said address electrode is a lower address electrode.

9. An image projection system comprising:

a light source for providing a beam of light along a first path;

micromirror device on said first path, said micromirror device comprising;

a substrate;

an address electrode supported by said substrate;

a deflectable member supported by said substrate and spaced apart from said address electrode by a gap, said deflectable member operable to rotate around a hinge axis between an undeflected position and at least one deflected position;

said address electrode having a beveled surface to form a narrow first region of said gap and a wider second region of said gap farther from said hinge axis than said first region when said deflectable member is in said deflectable position; and

a controller for providing image data to said micromirror device, said image data directing said micromirror device to rotate said deflectable member to either a first position wherein light incident said deflectable member is directed along a second path to an image plane, or to rotate said deflectable member to a second position wherein light incident said deflectable member is directed along a third path away from said image plane.

10. The image projection system of claim 9, wherein said address electrode is an upper address electrode.

11. The image projection system of claim 9, wherein said address electrode is a lower address electrode.

12. An image projection system comprising:

a light source for providing a beam of light along a first path;

micromirror device on said first path, said micromirror device comprising;

a substrate;

an address electrode supported by said substrate;

a deflectable member supported by said substrate and spaced apart from said address electrode by a gap, said deflectable member operable to rotate around a hinge axis between an undeflected position and at least one deflected position;

said address electrode having a stair stepped surface to form a narrow first region of said gap and a wider second region of said gap farther from said hinge axis than said first region when said deflectable member is in said undeflected position; and

a controller for providing image data to said micromirror device, said image data directing said micromirror device to rotate said deflectable member to either a first position wherein light incident said deflectable member is directed along a second path to an image plane, or to rotate said deflectable member to a second position wherein light incident said deflectable member is directed along a third path away from said image plane.

13. The micromirror device of claim 12, said stair stepped surface formed by encapsulating an oxide layer between two metal layers.

14. The image projection system of claim 12, wherein said address electrode is an upper address electrode.

15. The image projection system of claim 12, wherein said address electrode is a lower address electrode.

16. A micromechanical device having improved electrostatic efficiency, said device comprising:

a first member forming one half of an air-gap capacitor; and

a second member forming one half of an air gap capacitor, said second member spaced apart from said first member by an air gap, said first member operable to deflect between an undeflected position and at least one deflected position, said second member having a stair stepped surface such that said air gap is smaller in a first region than in a second region when said second member is in said undeflected state.

17. The micromechanical device of claim 16, said stair stepped surface of said second member formed by encapsulating an oxide layer.