US 6,212,056 B1 · Micromachined variable capacitor

Abstract

First and second wafers are micromachined by standard integrated-circuit fabrication techniques to respectively make first and second component parts of a variable capacitor. A thin flexible membrane in the first wafer is integral with and mechanically supported by the first wafer. A metal pattern on the first wafer includes a first capacitor plate on the membrane. In the second wafer, a well is formed. A metal pattern on the second wafer includes a second capacitor plate in the well. By bonding the two parts together face-to-face, the capacitor plates are positioned in spaced-apart alignment with each other. External electrical connections to the plates are made via bonding-pad portions of the metal patterns on the wafers. In response to electrical control signals, the metal plate on the membrane can be moved toward the other plate, thereby selectively changing the capacitance of the assembly.

Claims12

Dependent claims

A variable capacitor comprising

a first wafer having a main planar surface,
a single-layer flexible membrane formed integral with said wafer and mechanically supported by said wafer only along the entire periphery of said membrane, the surface of said membrane comprising a portion of said main planar surface,
a first metal capacitor plate on the surface of said flexible membrane,
a second wafer having a main planar surface,
a well in the surface of said second wafer,
a second metal capacitor plate in said well,
said first and second wafers being bonded together such that the respective main planar surfaces thereof face each other and said first and second capacitor plates are in alignment with each other with an air-gap therebetween,
and metal patterns on said first and second wafers respectively connected to said first and second plates to provide bonding pads for electrical connections to said plates,
wherein said first wafer comprises single-crystal silicon, the surface of said silicon wafer constituting the main planar surface of said first wafer.

6 more elements

A variable capacitor comprising

a first wafer having a main planar surface,
a flexible membrane formed integral with said wafer and mechanically supported by said wafer only along the entire periphery of said membrane, the surface of said membrane comprising a portion of said main planar surface,
a first metal capacitor plate on the surface of said flexible membrane,
a second wafer having a main planar surface,
a well in the surface of said second wafer,
a second metal capacitor plate in said well,
said first and second wafers being bonded together such that the respective main planar surfaces thereof face each other and said first and second capacitor plates are in alignment with each other with an air-gap therebetween,
and metal patterns on said first and second wafers respectively connected to said first and second plates to provide bonding pads for electrical connections to said plates,
wherein an additional separate and distinct pair of facing spaced-apart metal plates are respectively formed on the surface of said flexible membane and in said well, the air-gap distance between said separate and distinct pair of plates being greater than the air-gap distance between the first and second capacitor plates, said additional pair of facing plates comprising the sole control instrumentality by which said flexible membrane is moved by electrostatic attraction to vary the distance and thus the capacitance between said first and second capacitor plates.

6 more elements

Dependencies are inferred from the claim text.

Micromachined variable capacitor

Life of this patent

Micromachined variable capacitor

Life of this patent

Abstract

Claims12