MEMS cavity-coating layers and methods

• US 7,733,552 B2
• Filed: 03/21/2007
• Issued: 06/08/2010
• Est. Priority Date: 03/21/2007
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Natarajan, Bangalore R., Gousev, Evgeni, Heald, David, Webster, James Randolph, Londergan, Ana R.
• Primary Examiner(s): Mack; Ricky L
• Assistant Examiner(s): Tra; Tuyen Q
• Application Number:
  US11/689,430
• Publication Number:
  US 20080231931A1
• Time in Patent Office: 1,175 Days
• Field of Search: 359/237, 359/245, 359/248, 359/254, 359/291, 359/292, 359/293, 359/295, 359/298
• US Class Current: 359/237
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• 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

Devices, methods, and systems comprising a MEMS device, for example, an interferometric modulator, that comprises a cavity in which a layer coats multiple surfaces. The layer is conformal or non-conformal. In some embodiments, the layer is formed by atomic layer deposition (ALD). Preferably, the layer comprises a dielectric material. In some embodiments, the MEMS device also exhibits improved characteristics, such as improved electrical insulation between moving electrodes, reduced stiction, and/or improved mechanical properties.

Claims

1. A method for forming an optical interferometric modulator, the method comprising:

forming a cavity in an optical interferometric modulator, wherein

the cavity is defined by a primary dielectric layer and a second layer, and

the second layer is reflective and movable relative to the primary dielectric layer; and

forming a supplemental dielectric layer as part of an optical dielectric layer within the cavity by atomic layer deposition (ALD) after forming the cavity, wherein the supplemental dielectric layer has a thickness of at least about 10 Å

over each of the primary dielectric layer and the second layer within the cavity, and wherein a total thickness of the optical dielectric layer depends upon the thicknesses of the supplemental dielectric layer and the primary dielectric layer.

2. The method of claim 1, wherein forming the supplemental dielectric layer comprises forming at least part of an optical oxide layer.

3. The method of claim 2, wherein forming the supplemental dielectric layer comprises forming at least one of Al₂O₃ and SiO₂.

4. The method of claim 2, wherein forming the supplemental dielectric layer comprises forming a plurality of sub-layers.

5. The method of claim 2, wherein forming the supplemental dielectric layer comprises forming at least part of the optical oxide layer at a temperature of less than about 350°

C.

6. The method of claim 1, wherein forming the supplemental dielectric layer by ALD comprises forming a first conformal layer of an optical oxide material within the cavity.

7. The method of claim 6, wherein a thickness of the first conformal layer formed over a portion of the primary dielectric layer defining the cavity is substantially equal to a thickness of the first conformal layer formed over a portion of the second layer defining the cavity.

8. The method of claim 7, wherein a thickness of the first conformal layer formed over a portion of the primary dielectric layer defining the cavity is from about 50 Å

to about 400 Å

.

9. The method of claim 1, further comprising forming a layer of an optical dielectric material on a surface of the second layer after forming the cavity, wherein the surface of the second layer is outside of the cavity.

10. The method of claim 1, wherein forming the supplemental dielectric layer by ALD comprises sealing at least one pinhole in the primary dielectric layer.

11. The method of claim 1, wherein a total thickness of the optical dielectric layer, which includes the supplemental dielectric layer and the primary dielectric layer, is less than about 100 nm.

12. The method of claim 1, wherein forming the supplemental dielectric layer by ALD comprises forming at least part of an optical oxide layer over a manufacturing residue disposed on the primary dielectric layer.

13. The method of claim 1, further comprising packaging the interferometric modulator before forming the supplemental dielectric layer by a method comprising:

forming a seal circumscribing the interferometric modulator, wherein the seal comprises at least one opening; and

securing a backplate to the seal, thereby packaging the optical interferometric modulator.

14. The method of claim 13, further comprising filling the at least one opening in the seal after forming the supplemental dielectric layer.

15. An optical interferometric modulator formed by the method of claim 1.

16. The method of claim 1, wherein the optical interferometric modulator is an element of an array of microelectromechanical systems devices.

17. The method of claim 16, further comprising forming a plurality of openings in the second layer.

18. A microelectromechanical systems device manufactured by the method of claim 16.