Electrostatic actuator for microelectromechanical systems and methods of fabrication

• US 7,261,826 B2
• Filed: 01/27/2004
• Issued: 08/28/2007
• Est. Priority Date: 02/03/2000
• Status: Expired due to Term

• Current Assignee: Calient Networks Incorporated
• Original Assignee: Calient Networks Incorporated
• Inventors: Adams, Scott, Davis, Tim, Miller, Scott, Shaw, Kevin, Chong, John Matthew, Lee, Seung Bok (Chris)
• Primary Examiner(s): Hassanzadeh; Parviz
• Assistant Examiner(s): CULBERT, ROBERTS P
• Application Number:
  US10/766,087
• Publication Number:
  US 20040246306A1
• Time in Patent Office: 1,309 Days
• Field of Search: 216/2, 216/11, 216/17, 216/20, 216/24, 216/33, 216/36, 438/22, 438/24, 438/48, 438/50, 438/52, 438/53, 438/689, 438/694, 438/696, 438/700, 438/702, 257414-419, 7351415-51439
• US Class Current: 216/2
• CPC Class Codes: H01H 2001/0068 with multi dimensional movement, i.e. the movable actuator performing movements in at least two different directions
• CPC Class Codes: H01H 67/22 Switches without multi-position wipers
• CPC Class Codes: H02N 1/008 Laterally driven motors, e.g. of the comb-drive type

Abstract

A method and apparatus are described that may be used to provide decoupled rotation of structures about different pivot points. The apparatus may include one or more fixed blades mounted to a frame or substrate, one or more movable blades mounted to each structure to be moved, and flexures on which the structures are suspended. Separate movable blades may be provided for each degree of freedom. When voltage is applied between the fixed and movable blades, the electrostatic attraction generates a force attracting movable blades toward blades that are fixed relative to the moveable blades, causing a structure to rotate about the flexures. The angle of rotation that results may be related to the size, number and spacing of the blades, the stiffness of the flexures and the magnitude of the voltage difference applied to the blades. The blades are fabricated using deep silicon etching.

Claims

1. A method for fabricating a microelectromechanical apparatus comprising:

forming a layer of dielectric material on a first side of the substrate;

forming on the first side of the substrate vertical isolation trenches containing dielectric material;

patterning a masking layer on a second side of the substrate that is opposite to the first side of the substrate;

forming vias on the first side of the substrate;

metallizing the first side of the substrate;

forming second trenches on the first side of the substrate to define structures;

deeply etching the second side of the substrate to form narrow blades;

after forming the narrow blades, bonding a base wafer to the second side of the substrate;

etching through the vias on the first side of the substrate to release the structures and to provide electrical isolation, wherein at least one of the narrow blades is isolated by one of the vertical isolation trenches, and wherein at least one of the narrow blades is coupled to one of the structures.

2. The method of claim 1, wherein the substrate comprises a silicon wafer.

3. The method of claim 1, wherein the dielectric material is silicon dioxide.

4. The method of claim 1, further comprising depositing a second metal layer on the first side of the substrate after metallizing the first side of the substrate in order to form a reflective surface.

5. The method of claim 1, further comprising forming a passivation layer on the first side of the substrate after metallizing the first side of the substrate.

6. The method of claim 1, further comprising attaching a protective lid to the first side of the substrate.

7. The method of claim 6, wherein the protective lid comprises glass.

8. A method for fabricating a microelectromechanical apparatus, comprising:

patterning a masking layer on a second side of a substrate having a first side that is opposite to the second side of the substrate;

deeply etching the second side of the substrate to form narrow blades;

after forming the narrow blades, fusion bonding a recessed base wafer to the second side of the substrate;

forming a layer of dielectric material on the first side of the substrate;

forming on the first side of the substrate vertical trenches containing dielectric material;

forming vias on the first side of the substrate;

metallizing the first side of the substrate;

forming second trenches on the first side of the substrate to define structures;

etching through the vias on the first side of the substrate to release the structures, wherein at least one of the narrow blades resides between two of the vertical trenches, and wherein at least one of the narrow blades is coupled to one of the structures.

9. The method of claim 8, wherein the substrate comprises a silicon wafer.

10. The method of claim 8, further comprising thinning the first side of the substrate prior to forming a layer of dielectric material on the first side of the substrate.

11. The method of claim 8, wherein the dielectric material is silicon dioxide.

12. The method of claim 8, further comprising depositing a second metal layer on the first side of the substrate after metallizing the first side of the substrate in order to form a reflective surface.

13. The method of claim 8, further comprising forming a passivation layer on the first side of the substrate after metallizing the first side of the substrate.

14. The method of claim 8, further comprising attaching a protective lid to the first side of the substrate.

15. The method of claim 14, wherein the protective lid comprises glass.

16. A method for fabricating a microelectromechanical apparatus comprising:

forming a layer of dielectric material on a first side of a silicon-on-insulator (SOI) substrate;

patterning a masking layer on a second side of the SOI substrate that is opposite to the first side of the SOI substrate;

forming vias on the first side of the SOI substrate that extend through a buried oxide layer of the SOI substrate;

metallizing the first side of the SOI substrate;

forming trenches on the first side of the SOI substrate to define structures;

forming a passivation layer on the first side of the substrate on metallization of the first side of the SOI substrate and on sidewalls of the vias and trenches of the first side of the SOI substrate;

deeply etching the second side of the SOI substrate to form narrow blades, wherein at least one narrow blade is coupled to one of the structures and wherein at least one narrow blade resides beneath at least one via;

after forming the narrow blades, bonding a base wafer to the second side of the SOI substrate;

etching through the vias on the first side of the substrate to release the structures.

17. The method of claim 16, wherein the SOI substrate comprises an SOI wafer.

18. The method of claim 16, further comprising using a frit glass seal to attach a glass protective lid to the first side of the SOI substrate.

19. The method of claim 16, wherein the dielectric material is silicon dioxide.

20. The method of claim 16, further comprising depositing a second metal layer on the first side of the SOI substrate after metallizing the first side of the SOI substrate in order to form a reflective surface.

21. The method of claim 16, wherein deeply etching the second side of the substrate to form narrow blades comprises etching to the buried oxide layer of the SOI substrate.

22. A method for fabricating a microelectromechanical apparatus, comprising:

patterning a masking layer on a second side of the substrate that is opposite to a first side of the substrate;

attaching a spacer substrate to the second side of the substrate resulting in cavities;

forming a layer of dielectric material on the first side of the substrate;

forming on the first side of the substrate vertical trenches containing dielectric material;

forming vias on the first side of the substrate;

metallizing the first side of the substrate;

forming second trenches on the first side of the substrate to define structures;

etching an opening through the spacer substrate to expose the masking layer on the second side of the substrate;

deeply etching the second side of the substrate to form narrow blades;

after forming the narrow blades, bonding a base wafer to the spacer substrate;

etching through the vias on the first side of the substrate to release the structures, wherein at least one of the narrow blades resides between two of the vertical trenches, and wherein at least one of the narrow blades is coupled to one of the structures.

23. The method of claim 22, wherein the substrate comprises a silicon wafer.

24. The method of claim 22, wherein the dielectric material is silicon dioxide.

25. The method of claim 22, further comprising depositing a second metal layer on the first side of the substrate after metallizing the first side of the substrate in order to form a reflective surface.

26. The method of claim 22, further comprising forming a passivation layer on the first side of the substrate after metallizing the first side of the substrate.

27. The method of claim 22, further comprising attaching a protective lid to the first side of the substrate.

28. The method of claim 27, wherein the protective lid comprises glass.