Barium strontium titanate thin films by multi-ion-beam reactive sputtering technique

Thin films of barium strontium titanate including BaTiO₃ and SrTiO₃ end members were deposited by the multi-ion-beam reactive sputtering (MIBERS) technique using alkaline earth oxides (BaO and SrO) and Ti-metal targets. The MIBERS technique showed convenient and flexible control of the film compositions. The dielectric constants of the films deposited on Pt-coated Si substrates showed thickness dependence. A dielectric constant of 219 at 100 kHz was found for 1.2-μm-thick films. A charge storage density of 15 fC/gmm ² at 5 V and a leakage current density of 5.8 μA/cm² at an electric field of 0.1 MV/cm can be obtained for 0.3-μm-thick films and are suitable for application to 64-Mb dynamic random access memories (DRAMs). A charge storage density greater than 30 fC/μm² is achievable provided that some extrinsic factors which lower the overall dielectric constant can be eliminated. The films can be used for higher-memory-density DRAMs