Micro-electromechanical voltage tunable capacitor and and filter devices
Disclosed are one-port and two-port voltage-tunable micro-electromechanical capacitors, switches, and filter devices. High aspect-ratio metal micromachining is used to implement very high quality factor (Q) tunable and fixed capacitors, fixed inductors, and low insertion loss tunable and fixed bandpass LC filters. The tunable capacitors can move in the plane of the substrate by the application of DC voltages and achieve greater than 100% of tuning. A combination of low-loss substrate and highest conductivity metal is used to achieve record high Q and low insertion loss at radio frequencies. The disclosed tunable capacitor structure can also be used as a micromechanical switch.
1. A voltage tunable micromechanical capacitor apparatus comprising:
a substrate;
a dielectric layer disposed on the substrate;
a fixed interdigitated conductive capacitor plate disposed on the dielectric layer;
a fixed interdigitated conductive actuator plate disposed on the dielectric layer; and
a laterally movable conductive shuttle disposed between the fixed interdigitated capacitor plate and the fixed interdigitated actuator plate that interconnects a laterally movable interdigitated capacitor plate with a laterally movable interdigitated actuator plate.
2. The apparatus recited in claim 1 wherein the shuttle comprises:
the laterally movable interdigitated conductive capacitor plate disposed between the fixed capacitor plate and the movable shuttle;
the laterally movable interdigitated conductive actuator plate disposed between the movable capacitor plate and the fixed actuator plate; and
a movable dielectric layer disposed between the movable capacitor plate and the movable actuator plate, providing mechanical connection between them.
3. The apparatus recited in claim 1 wherein the movable capacitor plate and actuator plate are separated from the dielectric layer by a gap.
4. The apparatus recited in claim 1 wherein the substrate has a backside cavity closely formed under the conductive interdigitated plates to reduce the substrate loss.
5. The apparatus recited in claim 1 wherein the substrate is selected from a group including silicon, CMOS, BiCMOS, gallium arsenide, indium phosphide, glass, ceramic, silicon carbide, sapphire, organic and polymer.
6. The apparatus recited in claim 1 wherein the conductive layer is selected from a group including silver, gold, aluminum, nickel and copper.
7. The apparatus recited in claim 1 wherein the dielectric layer is selected from a group including silicon dioxide, silicon nitride, hafnium dioxide, zirconium oxide and low-loss polymer.
8. The apparatus recited in claim 1 wherein the gap between the fixed and movable plates of the capacitor is smaller than the gap between the fixed and movable plates of the actuator.
9. Apparatus recited in claim 1 further comprising a dielectric layer that coats the conductive layer to further increase the capacitance.
10. Apparatus recited in claim 1 further comprising:
a first conductive layer disposed on the dielectric layer that forms a routing layer;
a second dielectric layer disposed on the first conductive layer and patterned to create access points and support points; and
wherein the conductive layer comprises a spiral inductor that is connected to the fixed interdigitated capacitor plate to create a voltage tunable inductor-capacitor tank circuit.
11. The apparatus recited in claim 10 wherein the routing conductive layer is selected from a group including polysilicon, silver, gold, aluminum, nickel, and copper.
12. The apparatus recited in claim 10 wherein the second dielectric layer is selected from a group including air, silicon dioxide, silicon nitride, hafnium dioxide, zirconium oxide, and polymer.
13. Apparatus recited in claim 1 wherein the conductive layer comprises a transmission line inductor that is connected to the fixed interdigitated capacitor plate to create a voltage tunable inductor-capacitor tank circuit.
14. The apparatus recited in claim 1 further comprising:
a first conductive layer disposed on the dielectric layer that forms a routing layer;
a second dielectric layer disposed on the first conductive layer and patterned to create access points and support points; and
wherein the conductive layer and the routing layer form a fixed capacitor that is connected to the fixed interdigitated capacitor plate to create a larger tunable capacitor.
15. The apparatus recited in claim 14 wherein the routing conductive layer is selected from a group including polysilicon, silver, gold, aluminum, nickel, and copper.
16. The apparatus recited in claim 14 wherein the second dielectric layer is selected from a group including air, silicon dioxide, silicon nitride, hafnium dioxide, zirconium oxide, and polymer.
17. The apparatus recited in claim 1 further comprising:
an encapsulating layer disposed on the dielectric layer that forms a semi-hermetic cavity surrounding the capacitor plate, the actuator plate and the shuttle.