A Ru–Pt alloy electrode to suppress leakage currents of dynamic random-access memory capacitors

Abstract

Rutile TiO2, a high temperature phase, has attracted interest as a capacitor dielectric in dynamic random-access memories (DRAMs). Despite its high dielectric constant of >80, large leakage currents caused by a low Schottky barrier height at the TiO2/electrode interface have hindered the use of rutile TiO2 as a commercial DRAM capacitor. Here, we propose a new Ru–Pt alloy electrode to increase the height of the Schottky barrier. The Ru–Pt mixed layer was grown by atomic layer deposition. The atomic ratio of Ru/Pt varied in the entire range from 100 at.% Ru to 100 at.% Pt. Rutile TiO2 films were inductively formed only on the Ru–Pt layer containing ≤43 at.% Pt, while anatase TiO2 films with a relatively low dielectric constant (∼40) were formed at Pt compositions > 63 at.%. The Ru–Pt (40–50 at.%) layer also attained an increase in work function of ∼0.3–0.4 eV, leading to an improvement in the leakage currents of the TiO2/Ru–Pt capacitor. These findings suggested that a Ru–Pt layer could serve as a promising electrode for next-generation DRAM capacitors.