Magnetically packaged optical MEMs device and method for making the same

• US 20020071166A1
• Filed: 12/07/2000
• Published: 06/13/2002
• Est. Priority Date: 12/07/2000
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Jin, Sungho, Soh, Hyongsok
• Granted Patent: US 6,574,026 B2
• Time in Patent Office: Days
• US Class Current: 359/224
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 7/0067 for controlling the passage of optical signals through the package
• CPC Class Codes: B81C 2203/058 Aligning components using methods not provided for in B81C2203/051 - B81C2203/052
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

In accordance with the invention, the component layer, the spacer and the actuator layer of a MEMs device are assembled at ambient temperature and held together in lateral alignment by upper and lower magnets. Such ambient temperature magnetic packaging greatly minimizes the undesirable exposure of the sensitive MEMs components to high temperatures. The resulting MEMs device exhibits the high dimensional accuracy and stability. In a preferred embodiment, the component layer comprises a layer of movable mirrors and a spacer aerodynamically and electrostatically isolates each mirror, minimizing cross-talk between adjacent mirrors.

Claims

1. A magnetically-packaged optical micro-electro-mechanical (MEMS) device comprising:

a) a mirror layer having a frame and at least one mirror, each mirror movably connected to the frame;

b) an actuator layer having at least one conductive path and at least one electrode, each electrode capable of inducing movement of the mirror;

c) at least one spacer to separate the mirror layer and the actuator layer by a vertical gap spacing, the spacer optionally being separate from or part of the mirror layer and/or the actuator layer;

d) a first body of magnetic material disposed distally with respect to the mirror layer or secured thereto;

e) a second body of magnetic material disposed distally with respect to the actuator layer or secured thereto;

f) wherein the mirror layer, spacer and actuator layer are held in laterally-aligned and vertically spaced relation by magnetic attractive force between the first and second bodies of magnetic material.

2. The MEMs device of claim 1 wherein the mirror layer and the actuator layer have facing surfaces, each having a planar configuration.

3. The MEMs devices of claim 1 wherein the mirror layer or the actuator layer has a mesa configuration.

4. The MEMs device of claim 1 wherein the mirror layer, the spacer, the actuator layer, and the first and second bodies are laterally self-aligned by alignment slots, protruding features, or stepped edges present in one or more of the layers or bodies.

5. The MEMs device of claim 1 wherein the spacer aerodynamically isolates the mirror by blocking at least 30% of the peripheral area underlying the mirror.

6. The MEMs device of claim 1 wherein the first body has a cavity to allow a light signal to reach the mirror surface.

7. The MEMs device of claim 6 wherein the first body has a thickness of at least 5% of the mirror diameter.

8. The MEMs device of claim 1 wherein the first body or the second body comprises soft magnetic material having a coercive force of less than 50 Oe.

9. The MEMs device of claim 1 wherein the first body or the second body comprises permanent magnetic material having a coercive force of at least 200 Oe.

10. The MEMs device of claim 1 wherein the second body has a mirror image pattern of the first body.

11. The MEMs device of claim 1 wherein the mirror layer comprises single crystal silicon.

12. The MEMs device of claim 1 wherein the mirror layer comprises polycrystalline silicon.

13. The MEMs device of claim 1 wherein the movable mirror comprises a coating of metal.

14. The MEMs device of claim 1 wherein the spacer has a coeffecient of thermal expansion (CTE) different from the mirror layer and the actuator layer by not more than 50%.

16. The device of claim 1 wherein the first and second bodies of magnetic material are resiliently coupled.

17. The device of claim 1 wherein the range of resilient coupling is at least 5 micrometers.

18. The device of claim 1 wherein the spacer is comprised of ferromagnetic material.

19. The device of claim 1 wherein the first body is distal with respect to the mirror layer and further comprises a transparent plate disposed between the first body and the mirror layer.

20. The device of claim 1 wherein the spacer includes walls defining a cavity below the mirror and the walls are conductive to electrostatically isolate the cavity.

21. The device of claim 1 wherein the walls substantially cover the peripheral area around the cavity to aerodynamically isolate the cavity.

36. An improved optical power gain equalizer system for dynamically reducing the variation of optical signal strength comprising a device according to claim 1.

37. An improved wavelength division multiplexing telecommunication system comprising a device according to claim 1.

38. An improved light signal switch for an optical telecommunication system comprising a device according to claim 1.

39. An improved variable optical attenuator for an optical telecommunication system comprising a device according to claim 1.

15. The MEMs device of 14 wherein the spacer comprise a material selected from Si, Mo, W, Zr, Hf, or Ta.

22. The method of assembling a MEMS optical cross-connect device at ambient temperature comprising the steps of:

a) providing a mirror layer comprising at least one movable, light-reflecting mirror which can be tilted by electrostatic actuation;

b) providing an actuation layer which contains at least one electrical circuit for moving the movable mirror;

c) disposing a spacer between the mirror layer and the actuator layer so as to provide a predetermined vertical spacing gap between them, the spacer optionally being separate from or part of the mirror layer and/or the actuator layer;

d) providing at least two magnetic covers; and

e) placing at least one magnetic cover distally outside the mirror layer and at least one magnetic cover distally outside the electrode layer, so that a magnetically attractive force between the covers maintains the assembled mirror layer, spacer and the actuator layer in lateral alignment.

23. The method of claim 22 wherein

a) one cover is temporarily magnetically fixed in position on a support platen;

b) the mirror layer, the actuator layer and the spacer are brought together on the platen and laterally aligned; and

c) the other cover is aligned with and lowered onto the mirror layer

24. The method of claim 22 wherein the of mirror layer and the actuator layer each have facing surfaces in a planar configuration.

25. The method of claim 22 wherein at least one of the mirror layer or the actuator layer has a mesa configuration.

26. The method of claim 22 wherein the mirror layer includes a plurality of mirrors and the spacer aerodynamically separates adjacent mirrors by blocking at least 30% of the peripheral area.

27. The method of claim 22 wherein the magnetic cover above the mirror layer has a cavity to allow the light signal to reach the mirror.

28. The method of claim 22 wherein at least one magnetic cover comprises a soft magnetic material with a coercive force of less than 50 Oe.

29. The method of claim 22 wherein at least one magnetic cover comprises a permanent magnetic material with a coercive force of at least 200 Oe.

30. The method of claim 22 wherein the mirror layer comprises single crystal silicon.

31. The method of claim 22 wherein the mirror layer comprises polycrystalline silicon.

32. The method of claim 22 wherein the mirror comprises a coating of light-reflecting metal.

33. The method of claim 22 wherein the spacer has a coefficient of thermal expansion (CTE) different from that of the mirror layer and the actuator layer by not more than 50%.

34. The method of claim 33 wherein the spacer material is selected from Si, Mo, W, Zr, Hf, or Ta.

35. The method of claim 22 wherein the assembly is performed at ambient temperature.

40. A magnetically-packaged optical micro-electro-mechanical (MEMS) device comprising:

a) a component layer having a frame and at least one component, each component movably connected to the frame;

b) an actuator layer having at least one conductive path and at least one electrode, each electrode capable of inducing movement of the component;

c) at least one spacer to separate the component layer and the actuator layer by a vertical gap spacing, the spacer optionally being separate from or part of the component layer and/or the actuator layer;

d) a first body of magnetic material disposed distally with respect to the component layer or secured thereto;

e) a second body of magnetic material disposed distally with respect to the actuator layer or secured thereto;

f) wherein the component layer, spacer and actuator layer are held in laterally-aligned and vertically spaced relation by magnetic attractive force between the first and second bodies of magnetic material.

41. The MEMs device of claim 40 wherein the component layer and the actuator layer have facing surfaces, each having a planar configuration.

42. The MEMs devices of claim 40 wherein the component layer or the actuator layer has a mesa configuration.

43. The MEMs device of claim 40 wherein the component layer, the spacer, the actuator layer, and the first and second bodies are laterally self-aligned by alignment slots, protruding features, or stepped edges present in one or more of the layers or bodies.

44. The MEMs device of claim 40 wherein the spacer aerodynamically isolates the component by blocking at least 30% of the peripheral area underlying the component.

45. The MEMs device of claim 40 wherein the first body has a cavity to allow a light signal to reach the component.

47. The method of claim 46 wherein

a) one cover is temporarily magnetically fixed in position on a support platen;

b) the component layer, the actuator layer and the spacer are brought together on the platen and laterally aligned; and

c) the other cover is aligned with and lowered onto the component layer.

48. The method of claim 46 wherein the component layer and the actuator layer each have facing surfaces in a planar configuration.

49. The method of claim 46 wherein at least one of the component layer or the actuator layer has a mesa configuration.

50. The method of claim 46 wherein the component layer includes a plurality of components and the spacer aerodynamically separates adjacent components by blocking at least 30% of the peripheral area.

46. The method of assembling a MEMS device at ambient temperature comprising the steps of:

a) providing a component layer comprising at least one movable, component which can be moved by electrostatic actuation;

b) providing an actuation layer which contains at least one electrical circuit for moving the movable component;

c) disposing a spacer between the component layer and the actuator layer so as to provide a predetermined vertical spacing gap between them, the spacer optionally being separate from or part of the component layer and/or the actuator layer;

d) providing at least two magnetic covers; and

e) placing at least one magnetic cover distally outside the component layer and at least one magnetic cover distally outside the electrode layer, so that a magnetically attractive force between the covers maintains the assembled component layer, spacer and the actuator layer in lateral alignment.