MEMS reflectors having tail portions that extend inside a recess and head portions that extend outside the recess and methods of forming same

• US 6,757,093 B2
• Filed: 05/20/2002
• Issued: 06/29/2004
• Est. Priority Date: 05/21/2001
• Status: Expired due to Fees

• Current Assignee: JDS Uniphase Corporation (Lumentum Holdings Inc.)
• Original Assignee: JDS Uniphase Corporation (Lumentum Holdings Inc.)
• Inventors: Wood, Robert L., Agrawal, Vivek
• Primary Examiner(s): Thompson, Timothy
• Application Number:
  US10/151,080
• Publication Number:
  US 20020171909A1
• Time in Patent Office: 771 Days
• Field of Search: 359/291, 359/290, 359/280, 385/17, 385/15, 385/16, 385/18, 385/19, 438/52, 257/415
• US Class Current: 359/291
• CPC Class Codes: B81B 2201/045 Optical switches
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81B 2203/058 Rotation out of a plane parallel to the substrate
• CPC Class Codes: B81B 3/004 Angular deflection
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/085 the reflecting means being moved or deformed by electromagnetic means

Abstract

A MEMs structure can include a recess in a substrate, the recess having a side wall and a floor. A tail portion of a moveable reflector is on the substrate and extends beyond the side wall of the recess opposite the recess floor and is configured to rotate into the recess. A head portion of the moveable reflector extends on the substrate outside the recess.

Claims

1. A microelectromechanical system (MEMS) structure comprising:

a substrate;

a recess in the substrate having a side wall and a floor; and

a moveable reflector having a tail portion on the substrate extending beyond the side wall opposite the recess floor configured to rotate into the recess, and a head portion extending on the substrate outside the recess; and

a hinge coupled to the moveable reflector and to the side wall to define an axis about which the moveable reflector is configured to rotate in a first direction into the recess to move the tail towards the side wall and to rotate in a second direction out of the recess to move the tail away from the side wall.

2. A MEMS structure according to claim 1 wherein the tail extends beyond a first portion of the side wall, the structure further comprising:

a latch member on the substrate extending, opposite the floor, beyond a second portion of the side wall opposite the first portion of the side wall, wherein the latch member holds the head away from the substrate to define a wedge shaped gap between the head and the substrate opposite the head.

3. A MEMS structure according to claim 2 further comprising:

a first electrode on the head; and

a second electrode on the substrate opposite the head, wherein the wedge shaped gap changes in response to a voltage applied across the first and second electrodes.

4. A MEMS structure according to claim 1 wherein the tail extends beyond a first portion of the side wall and wherein the hinge applies a first force to the moveable reflector to rotate the head towards the substrate outside the recess, the structure further comprising:

a latch member extending on the substrate opposite the floor from a second portion of the side wall opposite the first portion of the side wall, wherein a surface of the latch member that faces towards the floor contacts a surface of the tail that faces away from the floor to apply a second force to the moveable reflector opposite the first force to hold the head in a position away from the substrate.

5. A MEMS structure according to claim 4 wherein the moveable reflector is configured to rotate to a reflecting position wherein the tail contacts the side wall and the head is aligned with an optical radiation path parallel to the substrate in response to a magnetic force.

6. A MEMS structure according to claim 4 wherein the position comprises a first reflecting position to reflect incident optical radiation along a first reflected optical path, wherein the moveable reflector is configured to rotate the head towards the substrate to a second reflecting position separated from the substrate in response to an electrostatic force to reflect the incident optical radiation along a second reflected optical path.

7. A MEMS structure according to claim 5 further comprising:

at least one raised structure on a surface of the tail that contacts the side wall and that keeps an adjacent portion of the surface from contacting the side wall.

8. A MEMS structure according to claim 7 further comprising:

a first electrode on the side wall; and

a second electrode on the surface of the tail that contacts the side wall opposite the first electrode, wherein the surface of the tail that contacts the side wall is clamped to the side wall in response to a voltage applied across the first and second electrodes.

9. A MEMS structure according to claim 7 wherein the substrate functions as a first electrode located on the side wall;

and

a second electrode on the surface of the tail that contacts the side wall opposite the first electrode, wherein the surface of the tail that contacts the side wall is clamped to the side wall in response to a voltage applied across the first and second electrodes.

10. A MEMS structure according to claim 2 wherein the latch comprises a material and the hinge comprises the material.

11. A MEMS reflector in an Optical Cross Connect (OXC) switch comprising:

a substrate;

a recess in the substrate having a side wall and a floor;

a moveable reflector having a tail portion extending on the substrate beyond a first portion of the side wall opposite the recess floor configured to rotate into the recess and a head portion extending beyond the side wall on the substrate outside the recess;

a hinge coupled to the moveable reflector and to the side wall to define an axis about which the moveable reflector is configured to rotate in a first direction into the recess to move the tail towards the side wall and to rotate in a second direction out of the recess to move the tail away from the side wall; and

a latch member on the substrate extending opposite the floor beyond a second portion of the side wall opposite the first portion of the side wall to contact the tail, wherein the latch member holds the head away from the substrate to define a wedge shaped gap between the head and the substrate opposite the head.

12. A MEMS structure according to claim 11:

wherein the hinge applies a first force to the moveable reflector to rotate the head towards the substrate outside the recess; and

wherein a surface of the latch member that faces towards the floor contacts a surface of the tail that faces away from the floor to apply a second force to the moveable reflector opposite the first force to hold the head in a neutral position away from the substrate.

13. A MEMS structure according to claim 12 wherein the moveable reflector is configured to rotate to a reflecting position wherein the tail contacts the side wall and the head is aligned with an optical radiation path parallel to the substrate in response to a magnetic force.

14. A MEMS structure according to claim 12:

wherein the neutral position comprises a first reflecting position wherein the head is aligned with a first optical radiation path; and

wherein the moveable reflector is configured to rotate the head closer to substrate to a second reflecting position wherein the head is aligned with a second optical radiation path in response to an electrostatic force.

15. A MEMS structure according to claim 13 wherein the first reflecting position defines a first angle of about 18 degrees with the substrate and wherein the second reflecting position defines a second angle of about 12 degrees with the substrate.

16. A microelectromechanical system (MEMS) structure comprising:

a substrate;

a recess in the substrate having a side wall;

a moveable reflector on the substrate that pivots on the side wall and is cantilevered thereon to define a neutral position that avoids contact with the substrate; and

a latch member extending from the side wall opposite the moveable reflector, wherein the latch member contacts a portion of the moveable reflector to bias the moveable reflector into the neutral position.

17. A structure according to claim 16 wherein the neutral position defines a non-parallel shaped gap between the moveable reflector and the substrate.

18. A structure according to claim 17 wherein the non-parallel shaped gap comprises a wedge shaped gap.

19. A structure according to claim 16 wherein the neutral position comprises a mechanically biased position free of electromagnetic forces applied by the structure.

20. A structure according to claim 16 wherein the gap defines an angle of about 18 degrees with the substrate.

21. A method of forming a microelectromechanical system (MEMS) structure comprising:

forming a recess in a substrate, the recess having a side wall and a floor;

forming a moveable reflector having a tail portion on the substrate extending beyond the side wall opposite the recess floor and a head portion extending on the substrate beyond the side wall outside the recess; and

forming a hinge coupled to the moveable reflector and to the side wall to define an axis about which the moveable reflector is configured to rotate in a first direction into the recess to move the tail towards the side wall and to rotate in a second direction out of the recess to move the tail away from the side wall.

22. A method according to claim 21 wherein the tail extends beyond a first portion of the side wall, the method further comprising:

forming a latch member on the substrate extending, opposite the floor, beyond a second portion of the side wall opposite the first portion of the side wall, wherein the latch member holds the head away from the substrate to define a wedge shaped gap between the head and the substrate opposite the head.

23. A method according to claim 22 further comprising:

forming a first electrode on the head; and

forming a second electrode on the substrate opposite the head, wherein the wedge shaped gap changes in response to a voltage applied across the first and second electrodes.

24. A method according to claim 21 wherein the tail extends beyond a first portion of the side wall and wherein the hinge applies a first force to the moveable reflector to rotate the head towards the substrate outside the recess, the method further comprising:

forming a latch member extending on the substrate opposite the floor from a second portion of the side wall opposite the first portion of the side wall, wherein a surface of the latch member that faces towards the floor contacts a surface of the tail that faces away from the floor to apply a second force to the moveable reflector opposite the first force to hold the head in a position away from the substrate.