Method for fabricating a microelectromechanical bearing

• US 6,555,201 B1
• Filed: 05/15/2000
• Issued: 04/29/2003
• Est. Priority Date: 09/27/1996
• Status: Expired due to Term

• Current Assignee: MCNC, Inc.
• Original Assignee: MCNC, Inc.
• Inventors: Koester, David A., Dhuler, Vijayakumar R., Markus, Karen W., Walters, Mark D.
• Primary Examiner(s): Thibodeau, Paul
• Assistant Examiner(s): Paulraj, Christopher
• Application Number:
  US09/570,628
• Time in Patent Office: 1,079 Days
• Field of Search: 428/131, 428/141, 428/156, 428/137, 438/703, 438/704, 438/745, 438/756, 249/61, 249/114.1
• US Class Current: 428/137
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 2203/058 Rotation out of a plane parallel to the substrate
• CPC Class Codes: B81B 3/0051 For defining the movement, i.e. structures that guide or limit the movement of an element mechanical arrangements for preventing or damping vibration or shock H01H3/60
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: Y10S 359/90 Methods
• CPC Class Codes: Y10T 428/24273 including aperture
• CPC Class Codes: Y10T 428/24322 Composite web or sheet
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24479 including variation in thickness

Abstract

An electromechanical device includes a first frame having a first aperture therein, a second frame suspended in the first frame wherein the second frame has a second aperture therein, and a plate suspended in the second aperture. A first pair of beams support the second frame along a first axis relative to the first frame so that the second frame rotates about the first axis. A second pair of beams supports the plate along a second axis relative to the second frame so that the plate rotates about the second axis relative to the frame. The first and second axes preferably intersect at a 90° angle. A first actuator provides mechanical force for rotating the second frame relative to the first frame about the first axis. A second actuator provides mechanical force for rotating the plate relative to the second frame about the second axis. Accordingly, the plate can be independently rotated relative to the first axis and the second axis. Related methods are also disclosed.

Claims

1. A method for fabricating a microelectromechanical bearing, said method comprising the steps of:

forming a sacrificial layer on a substrate, said step comprising;

forming a first sacrificial sublayer on said substrate wherein said first sacrificial sublayer has a first etch rate; and

forming a second sacrificial sublayer on said first sacrificial sublayer, such that the first sacrificial layer is adjacent to the substrate and the second sacrificial layer is opposite said substrate, wherein said second sacrificial sublayer has a second etch rate that is greater than the first etch rate of the first sacrificial layer;

isotropically etching a partial hole through said second sacrificial sublayer down to said first sacrificial sublayer, wherein said partial hole does not expose said substrate;

filling said partial hole with a bearing material; and

removing said first and second sacrificial sublayers.

2. A method according to claim 1 wherein said step of isotropically etching said sacrificial layer forms said partial hole such that said partial hole has a concave bottom surface.

3. A method according to claim 2 wherein said step of filling said partial hole with said bearing material comprises forming a layer of said bearing material on said sacrificial layer.

4. A method according to claim 3 wherein said filling step is followed by the step of patterning said layer of said bearing material so that a beam extends from said partial hole.

5. A method according to claim 4 wherein said step of filling said partial hole is preceded by the step of forming a complete hole through said sacrificial layer exposing a portion of said substrate, wherein said step of forming said layer of said bearing material includes filling said complete hole with said bearing material and wherein said beam extends from said partial hole to said complete hole so that said beam is fixedly connected to said substrate after removing said sacrificial layer.

6. A method according to claim 1, wherein said first sacrificial sublayer comprises a thermal silicon oxide material.

7. A method according to claim 1, wherein said second sacrificial sublayer comprises a phosphorus silicate glass material.

8. A mold for fabricating a microelectromechanical bearing comprising:

a substrate;

a sacrificial layer disposed on said substrate having a top and bottom surface said bottom surface adjacent to said substrate, wherein said sacrificial layer comprises;

a first sacrificial sublayer having a first etch rate;

a second sacrificial sublayer located on said first sacrificial sublayer, wherein said first sacrificial layer is adjacent to said substrate and said second sacrificial layer is opposite said substrate, wherein said second sacrificial sublayer has a second etch rate that is greater than the first etch rate of the first sacrificial layer; and

a hole extending from the top surface of the sacrificial layer through said second sacrificial layer to said first sacrificial layer toward the second surface of the sacrificial layer, and wherein a bottom surface of the hole adjacent to the bottom surface of said sacrificial substrate is concave; and

a first layer of bearing material disposed in the hole of said sacrificial layer, wherein said sacrificial layer may be removed such that said first layer of bearing material forms a microelectromechanical bearing.

9. A mold according to claim 8, wherein said hole extends through said sacrificial layer exposing a portion of said substrate, and wherein said first layer of bearing material is in contact with and fixedly connected to said substrate.

10. A mold for fabricating a microelectromechanical bearing comprising:

a substrate;

a sacrificial layer disposed on said substrate that defines a hole extending at least partially through said sacrificial layer, wherein said sacrificial layer comprises;

a first sacrificial sublayer having a first etch rate; and

a second sacrificial sublayer located on said first sacrificial sublayer, wherein said first sacrificial layer is adjacent to said substrate and said second sacrificial layer is opposite said substrate, wherein said second sacrificial sublayer has a second etch rate that is greater than the first etch rate of the first sacrificial layer, and wherein said hole extends through said second sacrificial layer to said first sacrificial layer;

a first layer of bearing material disposed in the hole of said sacrificial layer, wherein said sacrificial layer may be removed such that said first layer of bearing material forms a microelectromechanical bearing; and

a second layer of bearing material located on said sacrificial layer adjacent to and in contact with said first layer of bearing material, wherein said second layer of bearing material extends from said partial hole to form a beam connected to said first layer of bearing material to thereby form a beam and a microelectromechanical bearing.

11. A mold for fabricating a microelectromechanical bearing comprising:

a substrate;

a sacrificial layer disposed on said substrate that defines a hole extending at least partially through said sacrificial layer, wherein said sacrificial layer comprises;

a first sacrificial sublayer having a first etch rate, wherein said first sacrificial sublayer comprises a thermal silicon oxide material; and

a second sacrificial sublayer located on said first sacrificial sublayer, wherein said first sacrificial layer is adjacent to said substrate and said second sacrificial layer is opposite said substrate, wherein said second sacrificial sublayer has a second etch rate that is greater than the first etch rate of the first sacrificial layer, and wherein said hole extends through said second sacrificial layer to said first sacrificial layer; and

a first layer of bearing material disposed in the hole of said sacrificial layer, wherein said sacrificial layer may be removed such that said first layer of bearing material forms a microelectromechanical bearing.

12. A mold for fabricating a microelectromechanical bearing comprising:

a substrate;

a sacrificial layer disposed on said substrate that defines a hole extending at least partially through said sacrificial layer, wherein said sacrificial layer comprises;

a first sacrificial sublayer having a first etch rate; and

a second sacrificial sublayer located on said first sacrificial sublayer, wherein said first sacrificial layer is adjacent to said substrate and said second sacrificial layer is opposite said substrate, wherein said second sacrificial sublayer has a second etch rate that is greater than the first etch rate of the first sacrificial layer, wherein said second sacrificial sublayer comprises a phosphorus silicate glass material, and wherein said hole extends through said second sacrificial layer to said first sacrificial layer; and

a first layer of bearing material disposed in the hole of said sacrificial layer, wherein said sacrificial layer may be removed such that said first layer of bearing material forms a microelectromechanical bearing.