MICROMACHINED PIEZOELECTRIC Z-AXIS GYROSCOPE

• US 20130333175A1
• Filed: 07/31/2013
• Published: 12/19/2013
• 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, Shenoy, Ravindra V., Black, Justin Phelps, Petersen, Kurt Edward, Ganapathi, Srinivasan Kodaganallur, Stephanou, Philip Jason
• Granted Patent: US 9,410,805 B2
• Time in Patent Office: Days
• US Class Current: 29/25.35
• 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 method of fabricating a gyroscope, comprising:

depositing conductive material 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 capable of 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 at least one pair of drive beams disposed on opposing sides of the sense frame, the drive beams capable of driving 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 capable of driving the second side of the drive frame in a second and opposing direction along the first axis;

forming a drive frame suspension capable of substantially restricting a drive motion of the drive frame to that of a substantially linear displacement along the first axis, wherein forming the drive frame suspension involves forming a plurality of flexures, each flexure of the plurality of flexures capable of coupling a pair of drive beams to the drive frame; and

forming a sense frame suspension capable of being compliant to rotation around a second axis orthogonal to the first axis.

2. The method of claim 1, wherein forming the plurality of sense beams includes:

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

depositing a piezoelectric layer on the first metal layer;

depositing a second metal layer on the piezoelectric layer; and

forming a third metal layer on the second metal layer.

3. The method of claim 2, wherein forming the third metal layer involves forming at least one of nickel, nickel-iron, nickel-cobalt, nickel-manganese, cobalt-iron, nickel-tungsten, palladium-nickel or palladium-cobalt on the second metal layer.

4. The method of claim 2, wherein forming the third metal layer involves electroplating.

5. The method of claim 4, wherein the electroplating involves depositing metal for the drive frame and the sense frame.

6. The method of claim 4, further including separating the substrate into a plurality of sub-panels prior to the electroplating.

7. The method of claim 1, further including forming the sense frame suspension to resist motion along the first axis.

8. The method of claim 1, wherein 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

forming the third metal layer on the seed layer.

9. The method of claim 8, wherein forming the seed layer involves forming at least one of nickel, a nickel alloy, copper or chrome/gold on the oxide layer.

10. The method of claim 1, further comprising encapsulating the gyroscope inside packaging.

11. The method of claim 10, wherein the encapsulating involves sealing the gyroscope inside the packaging.

12. The method of claim 11, wherein the sealing involves sealing the gyroscope substantially in a vacuum.

13. The method of claim 10, further comprising forming a portion of the conductive material into an electrical connection from the gyroscope inside the packaging to an area outside of the packaging.

14. The method of claim 10, further comprising forming a seal ring, wherein the encapsulating involves attaching a cover to the seal ring.

15. The method of claim 14, wherein the cover includes metal or glass.

16. The method of claim 14, further comprising forming an electrical pad outside of the seal ring, the electrical pad being capable of electrical connection with the conductive material.

17. The method of claim 1, wherein forming the sense frame and forming the drive frame includes:

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.

18. The method of claim 17, wherein forming the sense frame and forming the drive frame 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.

19. The method of claim 1, wherein the substrate is a glass substrate.

20. The method of claim 1, wherein the conductive material includes at least one of chrome, gold, aluminum, titanium/tungsten, platinum, silver, nickel, nickel alloys of cobalt, iron or manganese, titanium/gold, tantalum/silver or doped silicon.