High-frequency properties of SrTiO3 thin-film capacitors fabricated on polymer-coated alloy substrates

Low-temperature (200 °C) sputter deposition of SrTiO3 (STO) thin films by using ultrahigh-density ceramic target enabled us to fabricate capacitors on polyimide-isoindroquinazoline dione (PIQ)- or benzocyclobutene (BCB)-coated alloy substrates. Complex impedances of the capacitors were analyzed. Capacitances of the 0.01 mm2 area capacitors with 200-nm-thick STO films were around 22 pF and were not dependent on frequency up to 8 GHz. Leakage-current densities of the films were lower than 10−6 A/cm2 at an applied voltage of 10 V and dielectric loss tangents were lower than 10−6.