Micromachined devices with anti-levitation devices

• US 20020046603A1
• Filed: 12/17/2001
• Published: 04/25/2002
• Est. Priority Date: 09/02/1997
• Status: Active Grant

• Current Assignee: Donald W. Carow, John A. Geen
• Original Assignee: Donald W. Carow, John A. Geen
• Inventors: Geen, John A., Carow, Donald W.
• Granted Patent: US 6,481,284 B2
• Time in Patent Office: Days
• US Class Current: 73/504.02
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A micromachined gyroscope has first and second coplanar bodies suspended over a substrate and movable in their plane relative to the substrate. The first body is dithered along a dither axis and is movable relative to the second body on the dither axis, but is rigidly connected for movement along an axis transverse to the dither axis. The second body is anchored so that it is substantially inhibited from moving along the dither axis, but can move with the first body along the transverse axis. The gyro has stop members and an anti-levitation system for preventing failure.

Claims

1. A micromachined device comprising:

a substrate;

a first body suspended over the substrate in a plane parallel to the substrate and movable in the plane and relative to the substrate;

a first plurality of fingers extending in parallel away from the first body and coplanar with the first body;

a second plurality of fingers parallel to the first plurality of fingers and interdigitating with the first plurality of fingers; and

a first conductive member on the substrate under a first group of the first plurality of fingers and the second plurality of fingers, the first conductive member electrically coupled to the second plurality of fingers.

2. The device of claim 1, wherein the first and second pluralities of fingers include drive fingers for dithering the first body in a first direction wherein the device is packaged under ambient conditions.

3. The device of claim 1, further comprising a second conductive member formed on the substrate and under a second group of the first plurality of fingers and the second plurality of fingers different from the first group of fingers and including some of the first plurality of fingers and the second plurality of fingers, the second conductive member being held at a voltage different from the second plurality of fingers.

4. The device of claim 3, wherein the first plurality of fingers and second plurality of fingers are each arranged in a row, wherein the first plurality of fingers have a net downward force over the first conductive members and the second plurality of fingers have a net upward force over the second conductive members, the forces canceling to keep the first body in the plane.

5. The device of claim 1, wherein the first body is movable in the plane along a dither axis, the device further comprising a second body suspended over the substrate, the first and second bodies being coplanar in a first plane parallel to the substrate, the second body coupled to the first body such that the second body is substantially inhibited from moving relative to the substrate along the dither axis.

6. The device of claim 1, wherein the first body has a perimeter portion defining and surrounding an aperture.

7. The device of claim 6, wherein the first plurality of fingers extends inwardly from the first body into the aperture.

8. The device of claim 6, wherein the first body has at least one cross-piece extending from one part of the perimeter portion to another part of the perimeter portion to define a plurality of apertures.

9. The device of claim 8, wherein the first plurality of fingers extends inwardly from the cross-piece into at least two apertures.

10. The device of claim 5, wherein the first body surrounds the second body.

11. The device of claim 5, wherein the second body surrounds the first body.

12. The device of claim 1, further comprising a package, wherein the device is packaged under ambient conditions.

15. The device of claim 14, further comprising a third conductive member on the substrate and under a third portion of the first and second body and held at the voltage.

16. The device of claim 15, further comprising a fourth conductive member on the substrate and under a fourth portion of the first and second body and electrically coupled to the second body.

17. The device of claim 16, wherein the first, second, third, and fourth conductive members are arranged in a row, with each spaced from the other.

13. A micromachined device comprising:

a substrate;

a first body suspended over the substrate in a plane parallel to the substrate and movable in the plane and relative to the substrate;

a first plurality of fingers extending in parallel away from the first body and coplanar with the first body;

a second plurality of fingers parallel to the first plurality of fingers and interdigitating with the first plurality of fingers;

a conductive member formed on the substrate under a first group of the first plurality of fingers and the second plurality of fingers, the conductive member held at a DV voltage and creating a force whereby the first plurality of fingers are urged away from the substrate in a direction perpendicular to the plane;

means for electrically counteracting the force.

14. A micromachined device comprising:

a substrate;

a first body over the substrate;

a second body suspended over the substrate in a plane parallel to the substrate and movable in the plane and relative to the substrate and to the first body;

a first conductive member on the substrate under a portion of the first and second body and held at a voltage; and

a second conductive member formed on the substrate under a second portion of the first and second body and electrically coupled to the second body.