Digital optical switch apparatus and process for manufacturing same

• US 20030118277A1
• Filed: 10/18/2002
• Published: 06/26/2003
• Est. Priority Date: 10/19/2001
• Status: Active Grant

• Current Assignee: Input/Output Incorporated
• Original Assignee: Input/Output Incorporated
• Inventors: Yu, Duli, Goldberg, Howard, Yi, Taechung, Selvakumar, Arjun
• Granted Patent: US 7,236,279 B2
• Time in Patent Office: Days
• US Class Current: 385/18
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81C 1/00182 Arrangements of deformable or non-deformable structures, e.g. membrane and cavity for use in a transducer
• CPC Class Codes: B81C 2201/019 Bonding or gluing multiple substrate layers
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/3548 1xN switch, i.e. one input and a selectable single output of N possible outputs
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

The present invention provides a digital optical switch apparatus and process for manufacturing the apparatus. The apparatus includes a mirror assembly coupled to a top cap and to a bottom cap. The top and bottom caps each include one or more electrodes that, when energized with electrical energy, move a mirrored surface to one of a plurality of discrete positions. Mirror assemblies can be cascaded to create a packaged assembly having any multiple of discrete positions. The process includes planar micro-machining techniques to create isolated islands for electrical feed through. The process enables mechanical bonding of multiple tiers via a single bond region and through a bond-pad window.

Claims

1. A micromachined device, comprising:

a) a housing;

b) a support structure coupled to the housing;

c) a mass coupled to the support structure by a pair of single-gimbaled structures for providing rotational movement of the mass about first and second axes of rotation; and

d) a plurality electrodes coupled to the housing in a diagonal relationship, the electrodes when energized with electrical power providing a selectable force to the mass for moving the mass in one of a plurality of angular directions to a discrete stopping position.

2. The device of claim 1, wherein the single-gimbaled structures comprise T-shaped hinges.

3. The device of claim 1, wherein the housing comprises:

i) a bottom wafer;

ii) a middle wafer coupled to the bottom wafer; and

iii) a top wafer coupled to the middle wafer, the top cap wafer having a light-permitting window formed therein.

4. The device of claim 3, wherein the middle wafer includes the mass, the hinges and the support structure.

5. The device of claim 1, wherein the mass includes a mirrored surface adapted to reflect an incident light beam in any of the plurality of angular directions.

6. The device of claim 4, wherein the mass includes a mirrored surface adapted to reflect an incident light beam in any of the plurality of angular directions, the incident light beam entering through the top cap window.

7. The device of claim 6 further comprising an overlay coupled to the top cap, the overlay including a plurality of ports for allowing light to pass through the overlay.

8. The device of claim 7, wherein the plurality of ports include at least one entry port for directing the incident light beam toward the mirrored surface and at least one exit port for directing the reflected light from the mirrored surface.

9. The device of claim 1, wherein the mass includes one or more portions contacting the housing during angular movement to stop the angular movement such that the mass stops angular movement in the discrete angular position.

10. The device of claim 9, wherein the mass includes a mirrored surface adapted to reflect an incident light beam, the reflected light leaving the mirrored surface in a direction controlled by the angular position of the mirrored surface.

11. A micro-machined device for controllably directing a beam of light, the device comprising:

a) a mirror coupled to a support structure by a pair of single-gimbaled dual-axis hinges for providing rotational movement of the mass about first and second axes of rotation;

b) a top cap bonded to the mirror support structure and having therein a window to allow light to reach the mirror;

c) a bottom cap bonded to the mirror support structure;

d) a plurality of electrodes disposed on at least one of the top cap and the bottom cap, the electrodes when energized with electrical energy provide a selectable force to the mirror for moving the mirror in a plurality of angular directions, the mirror including one or more portions contacting at least one of the top cap and the bottom cap during angular movement to stop movement of the mirror such that the mirror position is one of a plurality of discrete predetermined angular positions.

12. The device of claim 11, wherein the plurality of electrodes comprises a first plurality of electrodes positioned on the top cap and a second plurality of electrodes positioned on the bottom cap.

13. The device of claim 11 further comprising an overlay coupled to the top cap, the overlay including a plurality of ports for allowing light to pass through the overlay.

14. The device of claim 13, wherein the plurality of ports include at least one entry port for directing the incident light beam toward the mirrored surface and at least one exit port for directing the reflected light from the mirrored surface.

15. The device of claim 11 further comprising a plurality of optic fibers for directing light into and from the device.

16. The device of claim 14, further comprising a plurality of optic fibers coupled to the ports for directing light.

17. The device of claim 11 further comprising a movement control structure disposed on the bottom cap to control movement of the mirror.

18. The device of claim 17, wherein the movement control structure is adapted to controllably damp movement of the mirror.

19. The device of claim 17, wherein the mirror contacts the movement control structure to reduce vertical mirror movement.

20. The device of claim 11, wherein the mirror further comprises a layer of material on a surface opposite the mirror surface, the material being selected to balance stress across the mirror to reduce mirror bowing.

21. A micro-machined device for controllably directing a beam of light, the device comprising a plurality of mirror assemblies, each mirror assembly comprising:

a) a mirror coupled to a support structure by a pair of single-gimbaled dual-axis hinges for providing rotational movement of the mass about first and second axes of rotation;

b) a top cap bonded to the mirror support structure and having therein a window to allow light to reach the mirror;

c) a bottom cap bonded to the mirror support structure; and

d) a plurality of electrodes disposed on at least one of the top cap and the bottom cap, the electrodes when energized with electrical energy provide a selectable force to the mirror for moving the mirror in a plurality of angular directions, the mirror including one or more portions contacting at least one of the top cap and the bottom cap during angular movement to stop movement of the mirror such that the mirror position is one of a plurality of discrete predetermined angular positions,

wherein light exiting a first mirror assembly is directed to enter a second mirror assembly.

22. The device of claim 21 further comprising a mirror fixed in relation to the first mirror assembly and the second mirror assembly to reflect light leaving the first mirror assembly toward the second mirror assembly.

23. The device of claim 21, wherein the first mirror assembly and the second mirror assembly are positioned substantially in a face-to-face relationship to allow light reflected from the first mirror assembly to enter the second mirror assembly.

24. The device of claim 21 further comprising a plurality of optic fibers coupled to the first mirror assembly and to the second mirror assembly for directing light leaving the first mirror assembly toward the second mirror assembly.

25. A multi-tiered micro-machined device having at least three tiers, comprising:

a) a first wafer tier having one or more electrically conductive first leads responsive to electrical energy applied to the first leads;

b) a second wafer tier having one or more electrically conductive second leads responsive to electrical energy applied to the second leads;

c) a middle wafer tier coupled between the first wafer tier and the second wafer tier, the middle wafer tier including electrically nonconductive portions, a first electrically conductive portion, a second electrically conductive portion and a third conductive portion, wherein the first conductive portion makes contact with the first leads and the second conductive portion makes contact with the second leads when the middle wafer the first wafer and the second wafer are coupled.

26. A device according to claim 25, wherein the first and second leads are electrical interconnects for connecting to electrical components disposed on the first and second wafers.

27. A device according to claim 25, wherein the first and second leads are electrodes for electrically energizing a microstructure.

28. A device according to claim 25, wherein the middle wafer further comprises a frame attached first wafer and to the second wafer.

29. A device according to claim 28, wherein the middle wafer further comprises a gimbaled microstructure suspended from the frame.

30. A device according to claim 29, wherein the gimbaled microstructure includes an electrically conductive portion.

31. A device according to claim 30, wherein the gimbaled microstructure provides a moving electrode energized by at least one conductive portion of the middle wafer.

32. A device according to claim 25, wherein one or more of the conductive portions are located on islands electrically isolated from other conductive portions.

33. A device according to claim 25, wherein one or more of the conductive portions are bond pads for connecting the device tiers to external devices.

34. A device according to claim 25, further comprising a bond pad disposed on one of the first and second wafers for connecting the corresponding first and second leads to external devices.

35. A device according to claim 25, wherein one of the first wafer includes a window providing access to the middle wafer and to the second wafer.

36. A planar fabrication method for creating a multi-tiered micro-machined device having at least three tiers, the method comprising:

a) fabricating a first wafer tier having one or more electrically conductive first leads responsive to electrical energy applied to the first leads;

b) fabricating a second wafer tier having one or more electrically conductive second leads responsive to electrical energy applied to the second leads;

c) fabricating a middle wafer tier including a first electrically conductive portion and a second electrically conductive portion;

d) coupling the middle wafer tier between the first wafer tier and the second wafer tier such that the first conductive portion makes contact with the second leads when the middle wafer the first wafer and the second wafer are coupled.

37. The method of claim 36, wherein prior to coupling the wafers fabricating the first wafer further comprises:

i) providing a first wafer substrate;

ii) applying an insulating layer to the first wafer substrate; and

iii) depositing an electrically conductive metal on at least a portion of the insulating layer to for the first leads.

38. The method of claim 36, wherein prior to coupling the wafers, fabricating the second wafer further comprises:

i) providing a second wafer substrate;

ii) etching an initial window into the substrate without completely penetrating the second wafer substrate;

iii) applying an insulating layer to one side of the second wafer substrate; and

iv) depositing electrically conductive metal on at least a portion of the insulating layer to form the second leads.

39. The method of claim 36, wherein, prior to coupling the wafers, fabricating the middle wafer further comprises:

i) providing a middle wafer substrate;

ii) applying a structural layer to the middle wafer substrate; and

iii) etching portions of the structural layer to create one or more electrically isolated islands.

40. The method of claim 36, wherein the middle wafer is coupled to the first wafer before coupling the second wafer to an opposite side of the middle wafer.

41. The method of claim 36, wherein the middle wafer is coupled to the second wafer before coupling the first wafer to an opposite side of the middle wafer.

42. The method of claim 40, wherein prior to coupling the middle wafer to the first wafer, fabricating the first wafer further comprises:

i) providing a first wafer substrate;

ii) applying an insulating layer to the first wafer substrate;

iii) depositing an electrically conductive metal on at least a portion of the insulating layer;

fabricating the middle wafer further comprises;

iv) providing a middle wafer substrate;

v) applying a structural layer to the middle wafer substrate;

vi) etching portions of the structural layer to create one or more electrically isolated islands;

fabricating the second wafer further comprises;

vii) providing a second wafer substrate;

viii) etching an initial window into the substrate without completely penetrating the second wafer substrate;

ix) applying an insulating layer to one side of the second wafer substrate;

x) depositing electrically conductive metal on at least a portion of the insulating layer;

the method further comprising;

e) bonding the middle wafer to the first wafer;

f) thinning the middle wafer substrate;

g) etching a portion of the middle wafer structural layer to provide access to the first leads;

h) depositing metal to remaining portions of the structural layer to form the first, second and third conductive portions;

i) bonding the second wafer to the middle wafer; and

j) etching the initial window through the second wafer substrate to form a window providing access to the first, second, and third conductive portions through the window.

43. The method of claim 36, wherein fabricating the middle wafer further comprises fabricating a moveable micro structure on a portion of the middle wafer.

44. The method of claim 43 further comprising forming a recess in each of the first and second wafers to allow movement of the micro structure.

45. The method of claim 44 further comprising forming a movement-control structure in the first wafer recess to control movement of the micro structure.

46. The method of claim 36, wherein

i) fabricating the first wafer includes etching a portion of the first wafer substrate to form a first recess having a movement-control structure and depositing metal in at least the first recess to form a plurality of first wafer electrodes;

ii) fabricating the second wafer includes etching a portion of the second wafer substrate to form a second recess and depositing metal on at least one surface of the second wafer to form a plurality of second wafer electrodes; and

iii) fabricating the middle wafer includes forming a gimbaled microstructure moveable in the first and second recesses when energy is applied to the first and second pluralities of electrodes.

47. The method of claim 46, wherein, prior to coupling the wafers, fabricating the middle wafer further comprises:

i) providing a middle wafer substrate;

ii) applying a first structural layer to the middle wafer substrate;

iii) applying a second structural layer to the first structural layer; and

iv) etching portions of the second structural layer to create one or more electrically isolated islands.

48. The method of claim 47 further comprising:

i) coupling the middle wafer to the second wafer;

ii) thinning the middle wafer substrate to the first structural layer;

iii) etching an initial window in the second wafer substrate leaving a portion of the substrate in place;

iv) depositing metal on the thinned middle wafer substrate to form bond pads;

v) separating the first structural at selected locations to allow movement;

vi) coupling the first wafer to the middle wafer opposite the second wafer; and

vii) etching the second wafer substrate at the initial window to open a window for accessing the micro structure.

49. The method of claim 46, wherein, prior to coupling the wafers, fabricating the middle wafer further comprises:

i) providing a middle wafer substrate;

ii) applying a first structural layer to the middle wafer substrate;

iii) applying a second structural layer to the first structural layer;

iv) etching portions of the second structural layer to create one or more electrically isolated islands; and

v) depositing metal on the islands for electrical bonding.

50. The method of claim 49 further comprising:

i) coupling the middle wafer to the second wafer;

ii) thinning the middle wafer substrate to the first structural layer;

iii) etching the second wafer substrate to form a window for accessing the micro structure;

iv) depositing metal on the thinned middle wafer substrate to form bond pads;

v) separating the first structural at selected locations to allow movement; and

vi) coupling the first wafer to the middle wafer opposite the second wafer.

51. A planar fabrication method for creating a multi-tiered micro-machined device, the method comprising:

a) providing a first substrate;

b) applying a first insulating layer to the first substrate;

c) patterning the first insulating layer to expose portions of the first substrate;

d) applying a second insulating layer to a second substrate;

e) patterning the second insulating layer to expose portions of the second substrate;

f) coupling the second substrate to the first substrate such that the first insulating layer is coupled to the second insulating layer;

g) etching selected portions of the second substrate to expose the patterned second insulating layer and portions of the first insulating layer, wherein the exposed portions of the second insulating layer serve as in-situ masks to shield areas covered by the mask;

h) depositing a material substantially uniformly on exposed surfaces from generally one direction such that areas shielded by the masks receive substantially no material deposited thereon.

52. The method of claim 51, wherein the masks are initially etched to be frangible, the method further comprising removing the mask after fabricating the device.

53. The method of claim 51, wherein the in-situ masks remain in the device after fabricating the device.