Improving Electrical Properties and Thermal Stability of (Ba,Sr)TiO3 Thin Films on Cu(Mg) Bottom Electrodes

Cu(Mg) alloy films have replaced pure Cu as bottom electrodes for (Ba,Sr)TiO 3 (BST) capacitors used in high-frequency devices. A combined BST/Cu(Mg) structure reduced the leakage current density to 3.0 × 10 -8 A/cm 2 at 1 MV/cm, and increased the breakdown field from 0.4 to 2.4 MV/cm at 10 -6 A/cm 2 , from the corresponding values of the BST/Cu structure. High-quality characteristics probably follow the formation of a self-aligned MgO layer following the deposition of a Cu(Mg) alloy by annealing in an oxygen ambient, yielding an electrode with an excellent diffusion barrier and electrical characteristics, which is therefore effective in a BST thin-film capacitor. Additionally, the bias temperature stress and time-dependent dielectric breakdown in ambient nitrogen at an electric field of up to 2 V at temperatures between 100 and 200 °C were considered to accelerate Cu + ion drift.