CAPACITIVE MEMS GYROSCOPE AND METHOD OF MAKING THE SAME

• US 20110005319A1
• Filed: 07/12/2010
• Published: 01/13/2011
• Est. Priority Date: 07/13/2009
• Status: Active Grant

• Current Assignee: XI'AN Yisheng Optoelectronics Technology Co., Ltd.
• Original Assignee: Jiangsu Lexvu Electronics Co., Ltd.
• Inventors: HUANG, Herb He
• Granted Patent: US 8,375,791 B2
• Time in Patent Office: Days
• US Class Current: 73/514.32
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure

Abstract

A capacitive MEMS gyroscope and a method of making the same are disclosed. The capacitive MEMS gyroscope comprises a semiconductor substrate and a suspended composite wheel. The semiconductor substrate comprises: a read-out circuitry; at least one bottom electrode disposed on top of the semiconductor substrate, centered to a rotation axis and electrically connected to the read-out circuitry; at least one contact pad disposed on the top of the semiconductor substrate, electrically to the read-out circuitry; the composite wheel, partially made of dielectric film and configured in suspension above and in parallel to the semiconductor substrate and centered to the rotation axis, comprises: at least one top electrode disposed on the composite wheel, aligned vertically with one of the bottom electrode, electrically to the read-out circuitry; at least one circumferential spring centered to the rotation axis, bridging the composite wheel and the semiconductor substrate and consisting of at least one top electrode which electrically connects the top electrode to the contact pad on the semiconductor substrate. The gyroscope of the present invention formed by depositing and photolithographically patterning has miniaturized size, low tolerance scope and high sensing accuracy, as well as low fabrication costs owing to special bulk MEMS fabrication device unnecessary.

Claims

1. A capacitive MEMS gyroscope, comprising a semiconductor substrate and a suspended composite wheel;

wherein the semiconductor substrate centered to a rotation axis, comprises;

a read-out circuitry;

at least one bottom electrode disposed on top of the semiconductor substrate electrically connected to the read-out circuitry;

at least one contact pad disposed on the top of the semiconductor substrate, electrically to the read-out circuitry;

the composite wheel, partially made of dielectric film and configured in suspension above and in parallel to the semiconductor substrate and centered to the rotation axis, comprises;

at least one top electrode disposed on the composite wheel, aligned vertically with one of the bottom electrode, electrically to the read-out circuitry;

at least one circumferential spring centered to the rotation axis, physically bridging the composite wheel and the semiconductor substrate and consisting of at least one top electrode lead which electrically connects the top electrode to the contact pad on the semiconductor substrate.

2. The capacitive MEMS gyroscope according to claim 1, wherein the semiconductor further comprises a protruding circular central island from the semiconductor substrate;

the composite wheel further comprises;

an outer ring centered to the rotation axis;

an inner ring centered to the rotation axis and surrounding the protruding circular central island; and

at least two radial beams physically connecting the inner ring to the outer ring from the rotation axis.

3. The capacitive MEMS gyroscope according to claim 2, wherein the at least one circumferential spring bridges the radial beams to the semiconductor substrate at the at least one contact pad.

4. The capacitive MEMS gyroscope according to claim 1, wherein the semiconductor substrate is made from any or combination of semiconductor materials including silicon, germanium, gallium and arsenic.

5. The capacitive MEMS gyroscope according to claim 1, wherein the at least one bottom electrode and contact pad are made from any or combination of aluminum, titanium, tantalum, copper, cobalt, nickel, platinum, tungsten, and their alloys.

6. The capacitive MEMS gyroscope according to claim 1, wherein the at least one top electrode and top electrode lead are made from any or combination of aluminum, titanium, tantalum, copper, cobalt, nickel, platinum, tungsten, and their alloys.

7. The capacitive MEMS gyroscope according to claim 2, wherein the inner ring, the radial beams, and the circumferential spring arm are made from any or combination of metals, including aluminum, titanium, tantalum, copper, cobalt, nickel, platinum and tungsten, and dielectric materials, including silicon oxide, nitride, oxynitride, carbon oxynitride, carbide and metal oxides.

8. The capacitive MEMS gyroscope according to claim 2, wherein the protruding circular central island is made from any or combination of metals and semiconductors, including aluminum, titanium, tantalum, copper, cobalt, nickel, platinum and tungsten, as well as silicon, germanium, and silicon germanium, and the dielectric material from any or combination of silicon oxide, nitride, oxynitride, carbon oxynitride, carbide and metal oxides.

9. The capacitive MEMS gyroscope according to claim 1, wherein the composite wheel further comprises at least one vertical space limiter, configured at the outer edge of the composite wheel, having a first spacing smaller than a second vertical spacing of the rest of the suspended composite wheel with the semiconductor substrate.

10. The capacitive MEMS gyroscope according to claim 1, wherein the read-out circuitry comprises complementary metal oxide semiconductor devices.

11. The capacitive MEMS gyroscope according to claim 1, wherein the at least one circumferential spring arm is shaped in a zigzag configuration along the circumference centered to the rotation axis.

12. A method of making the capacitive MEMS gyroscope of claim 1, comprising:

providing the semiconductor substrate with read-out circuitry formed on;

depositing and photolithographically forming the bottom electrode and the contact pad on top of the semiconductor substrate;

depositing and photolithographically patterning a first sacrificial film on the semiconductor substrate;

depositing and photolithographically forming the top electrode and the top electrode lead;

depositing and photolithographically patterning the suspend composite wheel;

removing the first sacrificial film.

13. The method according to claim 12, wherein depositing and photolithographically patterning the suspend composite wheel comprises:

depositing and photolithographically patterning the outer ring, the inner ring, radial beams, the protruding circular central island and circumferential spring.

14. The method according claim 12, wherein depositing and photolithographically forming the top electrode and the top electrode lead comprises:

depositing and photolithographically patterning a second sacrificial film on the semiconductor substrate, covering the first sacrificial film;

depositing and photolithographically forming the top electrode and the top electrode lead.

15. The method according to claim 14, wherein depositing and photolithographically patterning the suspend composite wheel and circumferential spring comprises:

depositing and photolithographically patterning the outer ring, the inner ring, radial beams, the protruding circular central island, the vertical space limiter and circumferential spring.

16. The method according to claim 15, further comprising removing the second sacrificial film after forming the composite wheel.

17. The method according to claim 16, wherein the first sacrificial film and the second sacrificial film are carbon films.

18. The method according to claim 17, wherein the depositing of the first sacrificial film and the second sacrificial film are by means of:

placing the semiconductor substrate in a reactor chamber;

introducing a carbon-containing process gas into the chamber and introducing a layer enhancing additive gas that enhances thermal properties of the carbon film;

generating a reentrant toroidal RF plasma current in a reentrant path that includes a process zone overlying the substrate by coupling a plasma RF source power to an external portion of the reentrant path; and

coupling RF plasma bias power or bias voltage to the semiconductor substrate.

19. The method according to claim 18, wherein the first sacrificial film and the second sacrificial film are etch-removed in a reactor chamber containing oxygen gas and plasma generated with a plasma source power.

20. The method according to claim 18, wherein the first sacrificial film and the second sacrificial film are etch-removed in a reactor chamber containing nitrogen gas and plasma generated with a plasma source power.