Atomic Layer Deposition of TiOx/Al2O3 Bilayer Structures for Resistive Switching Memory Applications

Abstract

The resistive switching (RS) properties of a thin Al2O3 layer and TiOx/Al2O3 bilayers integrated into TiN/metal oxide/Pt crossbar devices are investigated for future memristive device (ReRAM) applications. The oxide bilayer stack is realized in consecutive atomic layer deposition (ALD) processes at 300 °C without any post‐annealing step. Stoichiometric Al2O3 and oxygen‐deficient TiOx thin films are grown from dimethylaluminum isopropoxide [DMAI: (CH3)2AlOCH(CH3)2] and tetrakis‐dimethlyamido‐titanium [TDMAT: Ti(N(CH3)2)4], respectively, as the metal sources, and water as the oxygen source. High insulating characteristics are confirmed for as‐grown amorphous Al2O3 films with a dielectric permittivity of 8.0 and disruptive field strength of about 7 MV cm−1, whereas the oxygen‐deficient TiOx shows semiconducting behavior. The bipolar‐type RS characteristics of TiN/TiOx/Al2O3/Pt cells show a strong dependence on both oxide layer thicknesses. A stable OFF/ON state resistance ratio of about 105 is obtained for the bilayer structure of 5 nm TiOx and 3.7 nm Al2O3.