Optimisation of Surface Capacitance and Leakage Currents on Ion Beam Sputtered SrTiO₃-Based MIM Capacitors for Above IC Technology

Abstract

SrTiO₃ (STO) deposition was performed by Ion Beam Sputtering on Pt/TiO₂/SiO₂/Si substrates. We showed that curing annealing after top electrode deposition is essential to achieve low leakage currents. A decrease of the leakage currents for thinner STO layers was observed, due to grain boundaries roughness increase with STO layer thickness as it was demonstrated by AFM experiments in the TUNA mode. Characteristics suitable for high density capacitors integrated in Above IC technology were achieved: a 20 nm-STO layer crystallized at 450°C and cured after top electrode deposition displays a surface capacitance of 36 nF/mm², leakage currents of 10⁻⁷A/cm² at 1 MV/cm and a breakdown voltage of 6 V.