THE LATEST ADVANCES IN HIGH-DIELECTRIC THIN-FILM CAPACITOR TECHNOLOGY FOR GHz-RF DEVICES

ABSTRACT

We present parallel-plate (Ba,Sr)TiO₃ and SrTiO₃ thin-film capacitor technology on silicon for RF devices. The in-plane thermal stress that is critical to low expansive Si substrates can be controlled by tuning the sputtering deposition pressure, and a corresponding change in the permittivity due to the electrostrictive effect is observed. The high-frequency dielectric response analysis combined with the equivalent circuit model and electromagnetic simulation enables accurate estimation of the intrinsic dielectric properties, thus demonstrating the linear increase of dielectric loss with frequency. With the bias applied, an electromechanical resonance appears in the GHz band due to piezoelectric effect, which is reproduced using the finite element method.

Keywords:

• (Ba,Sr)TiO₃
• SrTiO₃
• capacitor
• stress
• dielectric loss
• piezoelectric resonance

ACKNOWLEDGMENT

The authors wish to thank H. Wakabayashi, K. Ohta, and K. Nakajima for sample preparation and the evaluation of high-frequency dielectric properties. We also thank E. Oyama for experimental assistance.