MEMS vertical comb structure with linear drive/pickoff

• US 9,493,344 B2
• Filed: 11/21/2011
• Issued: 11/15/2016
• Est. Priority Date: 11/23/2010
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Horning, Robert D., Supino, Ryan
• Primary Examiner(s): Williams, Hezron E
• Assistant Examiner(s): Zhong, Xin
• Application Number:
  US13/301,172
• Publication Number:
  US 20120130672A1
• Time in Patent Office: 1,821 Days
• Field of Search: 735/143.2, 735/041.2, 735/040.4, 735/041.4, 735/141.7, 735/141.8, 735/143.8
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/025 Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242
• CPC Class Codes: B81B 2203/0136 Comb structures
• CPC Class Codes: B81B 3/0086 Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

A MEMS sensor comprises a substrate and at least one proof mass having a first plurality of combs. The proof mass is coupled to the substrate via one or more suspension beams such that the proof mass and the first plurality of combs are movable. The MEMS sensor also comprises at least one anchor having a second plurality of combs. The anchor is coupled to the substrate such that the anchor and second plurality of combs are fixed in position relative to the substrate. The first plurality of combs are interleaved with the second plurality of combs. Each of the combs comprises a plurality of conductive layers electrically isolated from each other by one or more non-conductive layers. Each conductive layer is individually coupled to a respective electric potential such that capacitance between the combs varies approximately linearly with displacement of the movable combs in an out-of-plane direction.

Claims

1. A Micro-electro-mechanical system (MEMS) sensor, comprising:

a substrate;

at least one proof mass having a first plurality of combs, wherein the proof mass is coupled to the substrate via one or more suspension beams such that the proof mass and the first plurality of combs are movable;

at least one anchor having a second plurality of combs, wherein the anchor is coupled to the substrate such that the anchor and second plurality of combs are fixed in position relative to the substrate;

wherein the first plurality of combs are interleaved with the second plurality of combs;

wherein each of the combs in the first plurality of combs and the second plurality of combs comprises a plurality of conductive layers electrically isolated from each other by one or more non-conductive layers;

wherein each conductive layer is individually coupled to a respective electric potential such that at least one conductive layer of each of the combs in the first plurality of combs and the second plurality of combs is coupled to a first electric potential and at least one conductive layer of each of the combs in the first plurality of combs and the second plurality of combs is coupled to a second potential;

wherein individual application of the first and second electric potentials to the respective conductive layers creates an electric field configuration in which capacitance between the first plurality of combs and the second plurality of combs varies approximately linearly with displacement of the movable combs in an out-of-plane direction.

2. The MEMS sensor of claim 1, wherein each comb of the first and second plurality of combs comprises a first outer conductive layer, a second outer conductive layer, and an inner conductive layer.

3. The MEMS sensor of claim 2, wherein the first outer conductive layer of each comb of the first and second plurality of combs is coupled to a positive voltage;

wherein the second outer conductive layer of each comb of the first and second plurality of combs is coupled to ground; and

wherein the inner layer of each comb of the first plurality of combs is coupled to ground and the inner layer of each comb of the second plurality of combs is coupled to the positive voltage.

4. The MEMS sensor of claim 2, wherein the inner conductive layer of each comb of the first and second plurality of combs is thicker than the respective first and second outer conductive layers.

5. The MEMS sensor of claim 4, wherein the inner conductive layer has thickness between approximately 14-20 μ

m, and each of the first and second outer conductive layers has a thickness of approximately 2 μ

m.

6. The MEMS sensor of claim 1, wherein the combs of the first and second plurality of combs are comprised of silicon, the plurality of conductive layers comprising regions of doped silicon and the one or more non-conductive layers comprising regions of undoped silicon.

7. The MEMS sensor of claim 1, wherein the plurality of conductive layers in each comb do not have a uniform thickness.

8. An electronic system comprising:

an inertial measurement unit comprising one or more Micro-electro-mechanical system (MEMS) sensors configured to provide motion measurements; and

a processing unit configured to calculate a navigation solution based on the motion measurements received from the inertial measurement unit;

wherein the one or more MEMS sensors each comprise;

a plurality of fixed combs; and

a plurality of movable combs interleaved with the plurality of fixed combs;

wherein each of the plurality of fixed and movable combs comprises a plurality of conductive layers separated by one or more non-conductive layers, each conductive layer individually coupled to a respective voltage such that at least one conductive layer of each of the combs in the plurality of fixed combs and the plurality of moveable combs is coupled to a first voltage and at least one conductive layer of each of the combs in the plurality of fixed combs and the plurality of moveable combs is coupled to a second voltage;

wherein individual application of the first and second voltages to the respective conductive layers creates a vertical electric field configuration in which the capacitance between the plurality of fixed and movable combs varies approximately linearly with vertical displacement of the movable combs.

9. The electronic system of claim 8, wherein the plurality of conductive layers of each movable and fixed comb comprises:

first and second outer conductive layers, each outer conductive layer adjacent to an outer surface of the respective comb; and

at least one inner conductive layer.

10. The electronic system of claim 9, wherein the first outer conductive layer of each fixed and movable comb are coupled to ground;

wherein the second outer conductive layer of each fixed and movable comb are coupled to a positive voltage;

wherein the at least one inner conductive layer of the fixed combs is coupled to the positive voltage and the at least one inner conductive layer of the movable combs is coupled to ground.

11. The electronic system of claim 9, wherein the at least one inner conductive layer of each comb is thicker than each of the respective outer conductive layers.

12. The electronic system of claim 11, wherein the at least one inner conductive layer has thickness between approximately 14-20 μ

m, and each of the first and second outer conductive layers has a thickness of approximately 2 μ

m.

13. The electronic system of claim 8, wherein the fixed and movable combs are comprised of silicon;

wherein the plurality of conductive layers comprise regions of silicon doped with a ratio of dopant atoms to silicon atoms high enough that the regions are overall electrically conductive, wherein the one or more non-conductive layers comprise regions of silicon doped with a ratio of dopant atoms to silicon atoms low enough that the regions are overall electrically non-conductive.

14. The electronic system of claim 8, wherein the one or more non-conductive layers are thinner than each of the plurality of conductive layers.

15. The electronic system of claim 8, wherein the at least one MEMS sensor is a MEMS accelerometer.