Micro-electro-mechanical systems torsional drive

• US 20050002084A1
• Filed: 05/09/2002
• Published: 01/06/2005
• Est. Priority Date: 05/09/2001
• Status: Active Grant

• Current Assignee: Chang Feng Wan
• Original Assignee: Chang Feng Wan
• Inventors: Wan, Chang Feng
• Granted Patent: US 7,005,775 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: B81B 2201/033 Comb drives
• CPC Class Codes: B81B 2201/045 Optical switches
• CPC Class Codes: B81B 2203/058 Rotation out of a plane parallel to the substrate
• CPC Class Codes: B81B 3/0035 Constitution or structural means for controlling the movement of the flexible or deformable elements
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

The present invention is related to a novel micro-electro-mechanical systems (MEMS) torsional drive that is capable of tilting suspended structure such as a micro-mirror for steering light beams in three-dimensional analog fashion, which is suitable for high port count optical switches. The torsional drive has the advantages of allowing large tilt angle, having low drive voltage, and capable of providing a feedback signal for closed-loop control.

Claims

1. A torsional drive, comprising:

a fixed comb; and

a movable comb and posts, wherein the movable comb hinges on torsion beams that are supported with said posts, said fixed comb and said movable comb interdigit slightly.

2. The torsional drive of claim 1, further comprising a substrate and posts, wherein said torsion beams are supported with posts, said posts and said fixed comb are anchored on a substrate with pedestals.

3. The torsional drive of claim 1, wherein said fixed comb, said movable comb and said posts are made from a doped silicon layer of 40 to 200 micrometers thick.

4. The torsional drive of claim 2, wherein said pedestals comprise an epoxy that is used as sacrificial layer and an adhesion layer.

5. The torsional drive of claim 2, wherein said pedestals comprise metal interconnects that make electrical connection from said fixed comb and said post to said substrate.

6. The torsional drive of claim 1, wherein said torsion beams comprises doped polycrystalline silicon.

7. The torsional drive of claim 1, further comprising a payload plate having a plurality of said torsional drives attached thereto, enabling said payload plate to turn both clockwise and counter-clockwise.

8. A torsional drive, comprising:

a payload plate;

a suspended frame;

inner fixed combs;

outer fixed combs;

inner torsion beams and outer torsion beams; and

inner movable combs and outer movable combs and posts, wherein said inner movable combs that are attached to said payload plate, are hinged on said suspended frame with torsion beams, and interdigit slight with said inner fixed combs slightly, and wherein inner fixed combs and outer movable combs are fixed to said suspended frame.

9. The torsional drive of claim 8, wherein said outer movable combs hinge on said outer torsion beams that are supported by said posts and are anchored on a substrate.

10. The torsional drive of claim 9 wherein said outer fixed combs and outer movable combs interdigit slightly and said inner torsion beams and said outer torsion beams are substantially perpendicular to each other.

11. The torsional drive of claim 10 wherein said suspended frame, said inner fixed combs, said outer torsion beams, said outer movable comb, and said posts are electrically grounded and a layer of insulator is deposited thereon.

12. The torsional drive of claim 11 wherein said inner torsion beams are electrically insulated from said suspended frame and said payload plate.

13. The torsional drive of claim 12 wherein said outer hinges are connected to inner movable combs and thin metal lines make electrical connections between the inner movable combs and bond pads on said posts.

14. The torsional drive of claim 8 further comprising a folded beam hinge having thin films with stresses deposited on selected runs of said folded beam.

15. The torsional drive including stressed folded beams of claim 14 that are supported with posts, further comprising a payload plate with movable combs attached thereon and fixed combs, wherein said movable combs and fixed combs interdigit with an offset angle but are not in direct contact.

16. A MEMS device, comprising:

a payload plate;

a suspended frame; and

inner fixed combs, outer fixed combs, inner stressed folded beam hinges, outer stressed folded beam hinges, inner movable combs, outer movable combs, and posts, wherein said inner fixed combs and said outer movable combs are fixed to said suspended frame, inner movable combs are attached to said payload plate, which is hinged on said suspended frame with said inner stressed folded beam hinges, and interdigit with said inner fixed combs with an offset angle.

17. The MEMS device of claim 16 wherein said outer movable combs hinge on said outer stressed folded beam hinges that are supported by said posts that are anchored on a substrate and wherein said outer fixed combs and outer movable combs interdigit slightly with an offset angle.

18. The MEMS device of claim 17 wherein said inner stressed folded beam hinges and said outer stressed folded beam hinges are perpendicular to each other and wherein said suspended frame, said inner fixed combs, said outer stressed folded beam hinges, said outer movable comb, and said posts are electrically grounded and a layer of insulator is deposited thereon.

21. The MEMS device of claim 16, wherein said payload plate comprises at least one optical mirror.

19. The MEMS device of claim 19 wherein said inner stressed folded beam hinges are electrically insulated from said suspended frame and said payload plate and said outer stressed folded beam hinges are electrically connected to inner movable combs and wherein thin metal lines make electrical connections between the inner movable combs and bond pads on said posts.

20. MEMS device in claim 19, wherein said suspended frame further comprises an inner frame underneath and supports said inner stressed folded beam hinges;

said inner frame is insulated from said inner stressed folded beam hinges;

said posts further comprises an outer frame underneath and supports said outer stressed folded beam hinges;

said outer frame is insulated from said outer stressed folded beam hinges;

22. A method of manufacturing a torsional drive, comprising the steps of:

(a) depositing a thin film and formation of hinges and interconnect on a doped silicon wafer;

(b) flip chip bump bonding to bond said wafer to a substrate wafer;

(c) epoxying to fill the void between said two bump bonded wafers;

(d) curing said wafers;

(d) patterning and etching said doped silicon wafer with a vertical trench etch; and

(e) removing said epoxy to release the top wafer to suspend said doped silicon wafer.