Micromachined piezoelectric z-axis gyroscope
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.
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 a combination of chrome and 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, a combination of titanium and tungsten, platinum, silver, nickel, nickel alloys of cobalt, iron or manganese, a combination of titanium and gold, a combination of tantalum and gold or doped silicon.