High-resolution in-plane tuning fork gyroscope and methods of fabrication

• US 7,043,985 B2
• Filed: 01/12/2005
• Issued: 05/16/2006
• Est. Priority Date: 01/13/2004
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Ayazi, Farrokh, Zaman, Mohammad Faisal
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US11/034,145
• Publication Number:
  US 20050150297A1
• Time in Patent Office: 489 Days
• Field of Search: 735/040.4, 735/040.2, 735/041.2, 735/041.3, 735/041.5, 735/041.6, 735/143.2, 295/92, 295/921
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

A microstructure comprising an in-plane solid-mass electrically conductive tuning fork gyroscope and fabrication methods. The gyroscope is formed using substrate material having lower and upper layers sandwiching a sacrificial insulating layer. An exemplary gyroscope comprises a low-resistivity single-crystal silicon substrate having a lower support layer and an upper flexible support layer. Two opposed proof masses that are separated from the lower support layer lie in and are supported by the upper flexible support layer. Two drive electrodes are disposed adjacent to the proof masses and are insulatably supported by the lower support layer and are separated from the upper flexible support layer. Sense, balance and tuning electrodes are disposed adjacent to the proof masses and are insulatably supported by the lower support layer and are separated from the upper flexible support layer. The operational mode shapes are in-plane with the substrate surface and only measures angular motion that are orthogonal to the plane of the substrate. The microstructure flexural design enables the sense and the drive resonant frequencies to occur in close proximity of one another. This enables matched-mode operation of the device thereby ensuring maximum sensitivity.

Claims

1. A gyroscope comprising:

an electrically-conductive substrate comprising a lower support layer and an upper flexible support layer;

first and second separated proof masses lying in and supported by the upper flexible support layer that are separated from the lower support layer;

first and second drive electrodes disposed adjacent to the proof masses that are insulatably supported by the lower support layer and that are separated from the upper flexible support layer;

sense electrodes disposed adjacent to the proof masses that are insulatably supported by the lower support layer and that are separated from the upper flexible support layer; and

tuning electrodes disposed adjacent to the proof masses that are insulatably supported by the lower support layer and that are separated from the upper flexible support layer.

2. The gyroscope recited in claim 1 wherein the first and second drive electrodes are disposed adjacent distal ends of the proof masses.

3. The gyroscope recited in claim 1 wherein the sense electrodes and tuning electrodes are selectively disposed on lateral sides of the proof masses.

4. The gyroscope recited in claim 1 further comprising:

balancing electrodes insulatably supported by the lower support layer and laterally separated from the proof masses.

5. The gyroscope recited in claim 4 wherein the balancing electrodes are disposed adjacent lateral sides of the upper flexible support layer.

6. The gyroscope recited in claim 1 wherein adjacent ends of the respective proof masses and drive electrodes comprise pluralities of interdigitated projections that form comb drives.

7. The gyroscope recited in claim 1 wherein the lower support layer comprises one or more anchors that couple the upper flexible support layer to the lower support layer.

8. The gyroscope recited in claim 1 wherein drive and sense modes are operated at resonance.

9. A gyroscope comprising:

an electrically-conductive substrate comprising a lower support layer and an upper flexible support layer;

first and second separated proof masses lying in and supported by the upper flexible support layer that are separated from the lower support layer;

first and second drive electrodes disposed adjacent to the proof masses that are insulatably supported by the lower support layer and that are separated from the upper flexible support layer;

sense electrodes disposed adjacent to the proof masses that are insulatably supported by the lower support layer and that are separated from the upper flexible support layer; and

tuning electrodes disposed adjacent to the proof masses that are insulatably supported by the lower support layer and that are separated from the upper flexible support layer;

wherein drive and sense operational modes occur in a plane defined by the upper layer, and wherein resonant frequencies of in-plane operational modes of the gyroscope are in close proximity to one another to provide for matched mode operation.

10. A method of forming a gyroscope, comprising:

providing an electrically-conductive substrate comprising lower and upper layers having a sacrificial insulating layer disposed therebetween; and

patterning and etching the substrate to define first and second separated proof masses formed in the upper layer that are suspended above the lower layer, first and second drive electrodes formed in the upper layer and disposed adjacent to the proof masses that are supported by the insulating layer and the lower layer and that have portions thereof adjacent to the proof masses that are suspended above the lower layer, sense electrodes formed in the upper layer disposed adjacent to the proof masses that are supported by the insulating layer and the lower layer, and tuning electrodes formed in the upper layer disposed adjacent to the proof masses that are supported by the insulating layer and the lower layer.

11. The method recited in claim 10 wherein the patterning and etching comprises:

patterning and etching the lower layer in areas of the upper layer that correspond to the proof masses and the drive electrodes;

etching the sacrificial insulating layer exposed by patterning and etching the lower layer to remove the sacrificial insulating layer and expose the upper layer; and

patterning and etching the upper layer to define the first and second suspended separated proof masses, the first and second drive electrodes having suspended portions adjacent to the proof masses, the sense electrodes, and the tuning electrodes.

12. The method recited in claim 10 wherein drive and sense operational modes occur in a plane defined by the upper layer.