Spatial light modulator

• US 5,579,151 A
• Filed: 02/17/1995
• Issued: 11/26/1996
• Est. Priority Date: 02/17/1995
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Cho, Chih-Chen
• Primary Examiner(s): Hindi, Nabil Z.
• Assistant Examiner(s): BEY, DAWN MARIE
• Application Number:
  US08/390,189
• Time in Patent Office: 648 Days
• Field of Search: 359/298, 359/316, 359/318, 359/846, 359/847, 359/224, 359/290, 359/291
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A spatial light modulator includes a reflector which is electrostatically deflectable out of a normal position, whereat a supporting beam is unstressed, into a deflected position, whereat a portion of the mirror contacts a portion of a landing electrode at the same electrical potential as the reflector. An inorganic layer or solid lubricant is deposited on the contacting portions. After the modulator is operated for a period of time, the tendency of the reflector to stick or adhere to the landing electrode is diminished or eliminated by the layer so that the reflector is returned to its normal position without any reset signal or with a reset signal having a reasonably low value. Preferred materials for the layer are SiC, AlN or SiO₂.

Claims

1. A micromechanical device of the type which includes a movable element having a normal position set by a deformable beam in its undeformed state and a deflected position in which the beam is deformed and a portion of the element engages a portion of a stationary member, deformation of the beam storing therein energy which tends to return the element to the normal position, the element being selectively electrostatically movable into its deflected position;

the device comprising;

a deposit of an inorganic passivant on the stationary member at the portion that the element engages the stationary member, wherein the deposit is between about 0.5 nm and about 20 nm thick.

2. A device as in claim 1 wherein said passivant is mechanically strong, scratch resistant, and thermally and chemically stable.

3. A method of passivating a micromechanical device of the type which includes a movable element having a normal position set by a deformable beam in its undeformed state and a deflected position in which the beam is deformed and a portion of the element engages a portion of a stationary member, deformation of the beam storing therein energy which tends to return the element to the normal position, the element being selectively electrostatically attractable into its deflected position;

the method comprising;

depositing a sufficient thickness of an inorganic, mechanically strong, scratch-resistant, and thermally and chemically stable passivant on one or both of the engageable portions of the stationary member and the element to prevent or limit sticking of the element to the stationary member, wherein the thickness is between about 0.5 nm and about 20 nm.

4. A method as set forth in claim 3, wherein:

the passivant is SiC, AIN or SiC₂.

5. A method as set forth in claim 3, wherein:

deposition of the passivant is effected by RF magnetron sputtering.

6. A method as set forth in claim 3, wherein the element is fabricated of a light reflecting material.

7. A micromechanical device of the type which includes a movable element having a normal position set by a deformable beam in its undeformed state and a deflected position in which the beam is deformed and a portion of the element engages a portion of a stationary member, deformation of the beam storing therein energy which tends to return the element to the normal position, the element being selectively electrostatically movable into its deflected position;

the device comprising;

a deposit of an inorganic passivant on one or both of the engageable portions of the stationary member and the element, the passivant being SiC, AlN or SiO₂, wherein the deposit is between about 0.5 nm and about 20 nm thick.

8. A device as set forth in claim 7, wherein:

the passivant is deposited by RF magnetron sputtering.

9. A device as set forth in claim 7, wherein:

the passivant is SiC having a thickness of about 0.5 nm to about 5 nm.

10. A device as set forth in claim 7, wherein:

the passivant is AlN having a thickness of about 0.6 nm to about 7.5 nm.

11. A device as set forth in claim 7, wherein:

the passivant is SiO₂ having a thickness of about 0.5 nm to about 20 nm.

12. A device as set forth in claim 7, wherein:

the deposit also resides on the beam.

13. A device as set forth in claim 7, wherein:

the element is a mirror element and the device functions as a spatial light modulator.

14. A spatial light modulator of the type which includes a movable mirror element having a normal position set by a deformable beam in its undeformed state and a deflected position in which the beam is deformed and a portion of the mirror element engages a portion of a stationary member, deformation of the beam storing therein energy which tends to return the mirror element to the normal position, the mirror element being selectively electrostatically attractable into its deflected position;

the DMD comprising;

a deposit of an inorganic, mechanically strong, scratch resistant, and thermally and chemically stable passivant on one or both of the engageable portions of the stationary member and the mirror element, wherein the passivant is SiC, AlN or SiO₂, wherein the deposit is between about 0.5 nm and about 20 nm thick.

15. A spatial light modulator as set forth in claim 14 wherein:

the passivant is deposited by RF magnetron sputtering.

16. A DMD as set forth in claim 14, wherein:

the deposit also resides on the beam.