Capacitive MEMS gyroscope and method of making the same
View Patent ↗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.
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 arm 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 substrate 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 arm 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 an 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 a circumference centered to the rotation axis.