Micromachined piezoelectric X-axis gyroscope

• US 20110265565A1
• Filed: 12/30/2010
• Published: 11/03/2011
• Est. Priority Date: 04/30/2010
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Acar, Cenk, Ganapathi, Srinivasan Kodaganallur, Shenoy, Ravindra Vaman, Stephanou, Philip Jason, Black, Justin Phelps, Petersen, Kurt Edward
• Granted Patent: US 8,584,522 B2
• Time in Patent Office: Days
• US Class Current: 73/504.08
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01C 19/5769 Manufacturing; Mounting; Housings
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/082 for two degrees of freedom of movement of a single mass
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/92247 the second connecting process involving a wire connector
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/19107 off-chip wires
• CPC Class Codes: H10N 30/03 Assembling devices that include piezoelectric or electrostrictive parts
• CPC Class Codes: H10N 30/071 Mounting of piezoelectric or electrostrictive parts together with semiconductor elements, or other circuit elements, on a common substrate
• CPC Class Codes: H10N 30/072 by laminating or bonding of piezoelectric or electrostrictive bodies
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49002 : Electrical device making
• CPC Class Codes: Y10T 29/49005 : Acoustic transducer
• CPC Class Codes: Y10T 29/49155 : Manufacturing circuit on or in base

Abstract

This disclosure provides systems, methods and apparatus, including computer programs encoded on computer storage media, for making and using gyroscopes. Some gyroscopes include a drive frame, a central anchor and a plurality of drive beams disposed on opposing sides of the central anchor. The drive beams may connect the drive frame to the central anchor. The drive beams may include a piezoelectric layer and may be configured to cause the drive frame to oscillate torsionally in a plane of the drive beams. The gyroscope may also include a proof mass and a plurality of piezoelectric sense beams. At least some components may be formed from plated metal. The drive frame may be disposed within the proof mass. The drive beams may constrain the drive frame to rotate substantially in the plane of the drive beams. Such devices may be included in a mobile device, such as a mobile display device.

Claims

1. A gyroscope, comprising:

a drive frame;

a central anchor;

a plurality of drive beams disposed on opposing sides of the central anchor, the drive beams connecting the drive frame to the central anchor, each of the drive beams including a piezoelectric layer and configured to cause the drive frame to oscillate torsionally in a plane of the drive beams;

a proof mass; and

a plurality of sense beams including a layer of piezoelectric sense electrodes, the sense beams configured for connecting the drive frame to the proof mass, the sense beams being configured to bend in a sense plane substantially perpendicular to the plane of the drive beams in response to an applied angular rotation, causing a piezoelectric charge in the sense electrodes.

2. The gyroscope of claim 1, wherein the plurality of drive beams is further configured to constrain the drive frame to rotate substantially in the plane of the drive beams.

3. The gyroscope of claim 1, wherein the plurality of drive beams includes a first pair of drive beams disposed on a first side of the central anchor and a second pair of drive beams disposed on an opposing side of the central anchor.

4. The gyroscope of claim 1, wherein the drive frame is disposed within the proof mass.

5. The gyroscope of claim 1, wherein the sense beams are configured to bend in the sense plane in response to sense motion of the proof mass.

6. The gyroscope of claim 1, wherein the sense beams are loaded due to forces exerted by the drive beams.

7. The gyroscope of claim 1, wherein the sense beams are tapered sense beams having a width that decreases with increasing distance from the anchor.

8. The gyroscope of claim 1, wherein the proof mass is formed, at least in part, from plated metal.

9. The gyroscope of claim 3, wherein the first pair of drive beams and the second pair of drive beams are configured to generate drive oscillations via a differential piezoelectric drive.

10. The gyroscope of claim 5, wherein the drive frame is substantially decoupled from the sense motion of the proof mass.

11. The gyroscope of claim 7, wherein bending stresses along the tapered sense beams are substantially uniform with increasing distance from the anchors when the gyroscope is operating in a sense mode.

12. A gyroscope, comprising:

drive frame means;

a substrate;

anchor means connected to the substrate and disposed within the drive frame means;

drive means for connecting the drive frame means to the anchor means, the drive means configured to cause the drive frame means to oscillate torsionally in a plane of the drive means, the drive means being further configured to constrain the drive frame means to rotate substantially in the plane of the drive means;

proof mass means disposed around the drive means, the proof mass means configured for sense motions wherein the proof mass means bends in a sense plane in response to an applied angular rotation, the sense plane being substantially perpendicular to the plane of the drive means, the sense motions of the proof mass means being substantially decoupled from motions of the drive frame means; and

sense means for connecting the drive means to the proof mass means, the sense motions of the proof mass means causing a piezoelectric charge in the sense means.

13. The gyroscope of claim 12, wherein the drive means includes a first pair of drive beams disposed on a first side of the anchor means and a second pair of drive beams disposed on an opposing side of the anchor means.

14. The gyroscope of claim 12, the sense means being further configured to bend in the sense plane in response to the sense motions of the proof mass means.

15. The gyroscope of claim 12, wherein forces exerted by the drive means axially load the sense means.

16. A method of fabricating a gyroscope, the method comprising:

depositing electrodes on a substrate;

forming an anchor on the substrate;

forming a drive frame on the anchor;

forming pairs of drive beams on opposing sides of the anchor, the drive beams connecting the drive frame to the anchor, the drive beams being configured to constrain the drive frame to rotate substantially in the plane of the drive beams;

forming a proof mass around the drive frame; and

forming a plurality of sense beams that connect the drive frame to the proof mass, the sense beams being configured to allow sense motions of the proof mass in a sense plane substantially perpendicular to the plane of the drive beams in response to an applied angular rotation, the sense beams being configured to substantially decouple the sense motions of the proof mass means from motions of the drive frame.

17. The method of claim 16, wherein forming the drive beams includes the following:

depositing a first metal layer that is in contact with the electrodes;

depositing a piezoelectric layer on the first metal layer;

depositing a second metal layer on the piezoelectric layer; and

electroplating a third metal layer on the second metal layer.

18. The method of claim 16, wherein the process of forming the anchor includes:

etching through a sacrificial layer to expose the first metal layer;

depositing an oxide layer on the first metal layer;

forming a seed layer on the oxide layer; and

electroplating the third metal layer on the seed layer.

19. The method of claim 16, wherein forming the proof mass and forming the drive frame include:

etching between a drive frame area and a proof mass area;

depositing high aspect ratio photoresist material between the drive frame area and the proof mass area; and

electroplating the third metal layer in the drive frame area and the proof mass area.

20. The method of claim 16, further including separating the substrate into a plurality of sub-panels prior to the electroplating.

21. The method of claim 19, wherein forming the proof mass and forming the drive frame also includes:

removing the high aspect ratio photoresist material from between the drive frame area and the proof mass area;

etching to expose a sacrificial layer disposed below the drive frame and the proof mass; and

removing the sacrificial layer to release the drive frame and the proof mass.

22. A gyroscope, comprising:

a central anchor;

a proof mass disposed around the central anchor, the proof mass having a first end and a second end;

a first drive beam connecting a first side of the central anchor to the first end of the proof mass;

a second drive beam connecting a second side of the central anchor to the second end of the proof mass;

a first pair of piezoelectric drive electrodes disposed on the first drive beam;

a second pair of piezoelectric drive electrodes disposed on the second drive beam;

a first piezoelectric sense electrode disposed on the first drive beam; and

a second piezoelectric sense electrode disposed on the second drive beam,

wherein the first pair and the second pair of piezoelectric drive electrodes are configured, via a differential piezoelectric drive, to cause the proof mass to oscillate torsionally in a plane of the drive beams, and

wherein the proof mass is configured for sense motions wherein the proof mass means bends in a sense plane in response to an applied angular rotation, the sense plane being substantially perpendicular to the plane of the drive beams, the sense motions of the proof mass causing a piezoelectric charge in the sense electrodes.

23. The gyroscope of claim 22, wherein each of the piezoelectric drive electrodes and the piezoelectric sense electrodes include a piezoelectric film.

24. The gyroscope of claim 22, wherein the proof mass is formed, at least in part, from plated metal.

25. The gyroscope of claim 22, wherein at least one of the first drive beam and the second drive beam include a central slot.

26. The gyroscope of claim 25, wherein the pairs of drive electrodes are disposed on opposite sides of the central slot.