MICROWAVE PROPERTIES OF FERROELECTRIC THIN-FILMS

The microwave properties of ferroelectric thin films are being investi gated. Interdigitated capacitors fabricated on ferroelectric thin film s of Sr0.5Ba0.5TiO3 have been characterized at room temperature from 5 0 MHz to 20 GHz, The relative dielectric constant and dielectric loss tangent of the ferroelectric thin film are then extracted using a conf ormal-mapping based approach. For large dielectric constants the upper frequency limit for which the conformal-mapping technique is valid ca n be as low as 5 GHz. This information is being used to optimize the f erroelectric film deposition process for microwave device application. Results indicate that this technology will compare favorably with con ventional varactors above a few GHz, and should be useful for tunable microwave circuits in some 300 K applications.