Low Temperature Hydrogen Induced Degradation of (Ba,Sr)TiO 3 Thin Film Capacitors

We have used electrical characterization and secondary ion mass spectroscopy (SIMS) to investigate the influence of hydrogen or deuterium (H/D) on the degradation of the electrical properties of metal/Ba0.7Sr0.3TiO3/metal (M/BSTO/M) thin film capacitors after forming gas annealing (FGA). Leakage and dielectric relaxation currents increase after FGA at temperatures as low as 23C. SIMS profiling shows that at 23C H/D diffuses through thin film metal electrodes and accumulates at electrode interfaces. The location (top or bottom electrode interface) of H/D accumulation is dependent on the type of electrodes and capacitor structure. The resulting asymmetric distribution of H/D leads to large voltage offsets in the C-V characteristic, asymmetric leakage currents, and increased dielectric relaxation currents. Possible mechanisms for increased leakage and relaxation currents after FGA are discussed.