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

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 degrees C without any post-annealing step. Stoichiometric Al2O3 and oxygen-deficient TiOx thin films are grown from dimethylaluminum isopropoxide [DMAI: (CH3)(2)AlOCH(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 10(5) is obtained for the bilayer structure of 5nm TiOx and 3.7nm Al2O3. The resistive switching of TiOx/Al2O3 bilayers integrated in mu-crossbar devices is investigated for future ReRAM. The bilayer stack is realized in consecutive atomic layer depositions (ALD) at 300 degrees C. Amorphous Al2O3 films exhibit a dielectric permittivity of 8.0 and disruptive field strength of 7 MV cm(-1), whereas the oxygen-deficient TiOx is semiconducting. The bipolar-type resistive switching characteristics of TiN/TiOx/Al2O3/Pt cells show a strong dependence on both oxide layer thicknesses.