Micromachined piezoelectric z-axis gyroscope

• US 20110265566A1
• 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 8,516,887 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• 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. Such gyroscopes may include a central anchor, a sense frame disposed around the central anchor, a plurality of sense beams configured for connecting the sense frame to the central anchor and a drive frame disposed around and coupled to the sense frame. The gyroscope may include pairs of drive beams disposed on opposing sides of the sense frame. The gyroscope may include a drive frame suspension for substantially restricting a drive motion of the drive frame to that of a substantially linear displacement along the first axis. The sense frame may be substantially decoupled from drive motions of the drive frame. Such devices may be included in a mobile device, such as a mobile display device.

Claims

1. A gyroscope, comprising:

a central anchor;

a sense frame disposed around the central anchor;

a plurality of sense beams configured for connecting the sense frame to the central anchor;

a drive frame disposed around and coupled to the sense frame, the drive frame including a first side and a second side;

a plurality of drive beams disposed on opposing sides of the sense frame, the drive beams configured to drive the first side of the drive frame in a first direction along a first axis substantially in the plane of the drive frame, the drive beams being further configured to drive the second side of the drive frame in a second and opposing direction along the first axis;

a drive frame suspension configured to substantially restrict a drive motion of the drive frame to that of a substantially linear displacement along the first axis; and

a sense frame suspension configured to be compliant to rotation around a second axis orthogonal to the first axis, the sense frame suspension configured to resist translational motion along the first axis.

2. The gyroscope of claim 1, wherein the sense frame is substantially decoupled from drive motions of the drive frame.

3. The gyroscope of claim 1, wherein the drive frame suspension includes a plurality of flexures configured for coupling the sense frame to the drive frame.

4. The gyroscope of claim 1, wherein the sense frame suspension includes a plurality of slots between the central anchor and the sense frame.

5. The gyroscope of claim 1, wherein the plurality of sense beams includes a first pair of sense beams extending from a first side of the central anchor along the first axis and a second pair of sense beams extending from a second side of the central anchor along a second axis substantially perpendicular to the first axis, the second side of the central anchor being adjacent to the first side of the central anchor.

6. The gyroscope of claim 1, wherein the plurality of drive beams includes pairs of drive beams on opposing sides of the sense frame.

7. The gyroscope of claim 1, further including an array of electrostatic actuators configured to tune a resonant frequency of drive frame motion.

8. The gyroscope of claim 1, wherein the drive frame includes a plurality of slots formed along an axis that is substantially perpendicular to the first axis.

9. The gyroscope of claim 1, wherein the drive beams and the sense beams include a piezoelectric layer.

10. The gyroscope of claim 1, wherein at least one of the sense frame and the drive frame are formed, at least in part, from plated metal.

11. The gyroscope of claim 5, wherein the sense frame suspension includes a slot extending:

along a first sense beam of the first pair of sense beams;

along the central anchor to the second pair of sense beams; and

along a second sense beam of the second pair of sense beams.

12. The gyroscope of claim 6, wherein the pairs of drive beams are disposed along a second axis that is substantially perpendicular to the first axis.

13. The gyroscope of claim 6, wherein the drive beams are configured to be actuated by applying anti-phase voltages to each pair of drive beams.

14. The gyroscope of claim 6, wherein the drive frame suspension includes a plurality of flexures, each flexure of the plurality of flexures configured for coupling a pair of drive beams to the drive frame.

15. The gyroscope of claim 7, wherein the array of electrostatic actuators is configured to suppress quadrature coupling from the drive frame to the sense frame.

16. A gyroscope, comprising:

central anchor means;

sense frame means disposed around the central anchor means;

sense beam means for detecting a sense motion of the gyroscope and for connecting the sense frame means to the central anchor means;

drive frame means disposed around and coupled to the sense frame means, the drive frame means including a first side and a second side;

drive means for driving the first side of the drive frame in a first direction along a first axis in the plane of the drive frame means and for driving a second side of the drive frame in a second and opposing direction along the first axis;

drive frame suspension means for substantially restricting a drive motion of the drive frame means to that of a substantially linear displacement along the first axis; and

sense frame suspension means for allowing rotation around a second axis orthogonal to the first axis and for resisting translational motion along the first axis.

17. The gyroscope of claim 16, wherein the drive means are disposed on opposing sides of the sense frame means.

18. The gyroscope of claim 16, wherein the sense frame means is substantially decoupled from drive motions of the drive frame means.

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

depositing electrodes on a substrate;

forming a central anchor;

forming a sense frame disposed around the central anchor;

forming a plurality of sense beams, each of the sense beams including piezoelectric sense electrodes, the sense beams configured for connecting the sense frame to the central anchor;

forming a drive frame disposed around and coupled to the sense frame, the drive frame including a first side and a second side;

forming a plurality of drive beams disposed on opposing sides of the sense frame, the drive beams configured to drive the first side of the drive frame in a first direction along a first axis in the plane of the drive frame, the drive beams being further configured to drive the second side of the drive frame in a second and opposing direction along the first axis;

forming a drive frame suspension configured to substantially restrict a drive motion of the drive frame to that of a substantially linear displacement along the first axis; and

forming a sense frame suspension configured to be compliant to rotation around a second axis orthogonal to the first axis.

20. The method of claim 19, wherein forming the plurality of sense 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.

21. The method of claim 19, further including forming the sense frame suspension to resist motion along the first axis.

22. The method of claim 19, wherein the process of forming the central 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.

23. The method of claim 19, wherein forming the sense frame and forming the drive frame include:

etching between a drive frame area and a sense frame area;

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

electroplating the third metal layer in the drive frame area and the sense frame area.

24. The method of claim 19, further including separating the substrate into a plurality of sub-panels prior to the electroplating.

25. The method of claim 27, wherein forming the sense frame and forming the drive frame also includes:

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

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

removing the sacrificial layer to release the drive frame and the sense frame.