Ferroelectric varactors suitable for capacitive shunt switching

A varactor shunt switch for microwave applications, the varactor shunt switch comprising:

• a high resistivity silicon layer;
• a silicon oxide layer on said high resistivity silicon layer;
• an adhesion layer on said silicon oxide layer;
• a metallic layer on said silicon oxide layer;
• a tunable ferroelectric thin-film dielectric layer on said metallic layer, wherein said tunable ferroelectric thin-film dielectric layer has a dielectric constant of greater or equal to about 200 at zero bias, an optimized dielectric constant of 1200, and a thickness of greater than 250 nm;
• and
• a top metal electrode on said tunable ferroelectric thin-film dielectric layer, wherein said top metal electrode defines a coplanar waveguide transmission line.

A method of fabricating a varactor shunt switch, the method comprising:

• depositing an adhesion layer on a high resistivity silicon substrate by electron-beam deposition and lift-off photolithography;
• depositing a metallic layer on said adhesion layer by sputtering and lift-off photolithography;
• covering said metallic layer with a layer of ferroelectric thin film by RF sputtering, wherein said metallic layer comprises of at least two ground conductors and a shunt conductor and said layer of ferroelectric thin-film has a dielectric constant of greater or equal to about 200 at zero bias, an optimized dielectric constant of 1200, and a thickness of greater than 250 μm;
• topping said layer of ferroelectric thin film with a top metal electrode by sputtering and lift-off photolithography, wherein said top metal electrode comprises of at least two ground conductor and a center conductor;
• and
• capping said top metal electrode with a coplanar waveguide transmission line comprised of at least two ground conductors and a signal strip.