Improving electrical properties and thermal stability of (Ba,Sr)TiO3 thin films on Cu(Mg) bottom electrodes

Abstract

Cu(Mg) alloy films have replaced pure Cu as bottom electrodes for (Ba,Sr)TiO3 (BST) capacitors used in high-frequency devices. A combined BST/Cu(Mg) structure reduced the leakage current density to 3.0 x 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 degrees C were considered to accelerate Cu+ ion drift.