BIDIRECTIONAL, OUT-OF-PLANE, COMB DRIVE ACCELEROMETER

• US 20100326191A1
• Filed: 06/26/2009
• Published: 12/30/2010
• Est. Priority Date: 06/26/2009
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Zhou, Shifang, Foster, Michael
• Granted Patent: US 8,418,555 B2
• Time in Patent Office: Days
• US Class Current: 73/514.29
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: Y10T 29/49009 Dynamoelectric machine

Abstract

A bi-directional, out-of-plane electrostatic comb drive apparatus including two electrically independent sets of stator comb tines; and a method for fabricating an out-of-plane comb drive with stacked sets of stator comb tines. A first set of stator comb tines is offset from a second set of stator comb tines. A set of rotor comb tines interleaves with both sets of stator comb tines. A first voltage applied to the first set of stator comb tines operates to pull the rotor tines toward the first set of stator comb tines. A second voltage applied to the second set of stator comb tines operates to pull the rotor tines toward the second set of stator comb tines, enabling bi-directional operation. A fabrication method is disclosed that enables fabrication of the first and second sets of stator comb tines that are mechanically and electrically independent and interleaved by the rotor comb tines.

Claims

1. An out-of-plane electrostatic comb drive accelerometer comprising:

a proof mass;

a plurality of rotor comb tines located at an edge of the proof mass;

a first plurality of stator comb tines interleaved with the plurality of rotor comb tines; and

a second plurality of stator comb tines interleaved with the plurality of rotor comb tines, wherein the first and second pluralities of stator comb tines are electrically isolated from one another, and wherein the first and second pluralities of stator comb tines are made from a single material layer.

2. The accelerometer of claim 1, wherein at least one tine of the first plurality of stator comb tines is in substantial alignment with at least one tine of the second plurality of stator comb tines in the out-of-plane direction.

3. The accelerometer of claim 1, wherein at least a portion of the first plurality of stator comb tines are aligned in substantially the same direction in a first plane, forming a first row, and wherein at least a portion of the second plurality of stator comb tines are aligned in substantially the same direction in a second same plane, forming a second row.

4. The accelerometer of claim 3, wherein the first plurality of stator comb tines forming a first row and the second plurality of stator comb tines forming the second row are substantially in alignment with one another.

5. The accelerometer of claim 3, wherein the first and second planes are substantially in parallel.

6. The accelerometer of claim 3, wherein the first plurality of stator comb tines forming the first row and the second plurality of stator comb tines forming the second row are separated by a space.

7. The accelerometer of claim 1, wherein the first plurality of stator comb tines is supported by an upper stator tine base, wherein the second plurality of stator comb tines is supported by a lower stator tine base, and wherein the upper and lower stator tine bases are mechanically and electrically isolated.

8. The accelerometer of claim 7, wherein the upper and lower stator tine bases are substantially the same thickness.

9. The accelerometer of claim 7, wherein the upper and lower stator tine bases are geometrically parallel in a direction perpendicular to the first and second planes.

10. The accelerometer of claim 1, wherein the thickness of an individual rotor comb tines is greater than the thickness of an individual stator comb tine.

11. The accelerometer of claim 1, wherein a first gap defines a first capacitance between the plurality of rotor comb tines and the first plurality of stator comb tines, wherein a second gap defines a second capacitance between the plurality of rotor comb tines and the second plurality of stator comb tines, and wherein a linear out-of-plane acceleration of the proof mass generates a torque about a rotational axis of the proof mass that changes the first capacitance and the second capacitance.

12. The accelerometer of claim 1, wherein a first voltage applied to the first plurality of stator comb tines pulls the rotor comb tines toward the first plurality of stator comb tines and a second voltage subsequently applied to the second plurality of stator comb tines pulls the rotor comb tines in an opposing direction toward the second plurality of stator comb tines.

13. The accelerometer of claim 1, further comprising:

a second plurality of rotor comb tines at a second edge of the proof mass;

a third plurality of stator comb tines interleaved with the second plurality of rotor comb tines; and

a fourth plurality of stator comb tines interleaved with the second plurality of rotor comb tines, wherein the third and fourth pluralities of stator comb tines are electrically isolated from one another, and wherein the third and fourth pluralities of stator comb tines are made from a single material layer.

14. The accelerometer of claim 1, further comprising a controller configured to apply a voltage to at least one of the plurality of interleaved rotor comb tines and stator comb tines, wherein the voltage changes a rebalancing force that opposes a rotational torque of the proof mass generated in response to an out-of-plane acceleration of the proof mass, wherein the controller is configured to determine an amount of acceleration based upon the applied voltage.

15. The accelerometer of claim 14, further comprising at least one flexure configured to couple the proof mass to an anchor, and configured to define an axis of rotation, wherein the rotational torque is about the axis of rotation.

16. A method for fabricating a comb drive, the method comprising:

performing a first anisotropic etch for exposing first portions of rotor tines and stator tines;

performing a second anisotropic etch for exposing remaining portions of the rotor tines, exterior edges of the stator tines and a plurality of passageways in the first portions of the stator tines;

performing a first isotropic etch for separating the first portion of each stator tine from a second portion of each stator tine, forming a first row of stator tines and a second row of stator tines;

performing a third anisotropic etch for partially separating bases of the first and second rows of stator tines; and

performing a fourth anisotropic etch for separating bases of the first and second rows of stator tines.