Atomic Layer Deposition of TiO_x/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.

Co-Design of ReRAM Passive Crossbar Arrays Integrated in 180 nm CMOS Technology

“…These cells show indeed a highly resistive HRS, a high forming voltage and an abrupt reset characteristic [22]. Consistent results for hybrid resistive switching layers have also been demonstrated in [23]. Zhang It is then conceivable that the is switching as well as the layer.…”

Spectromicroscopic insights for rational design of redox-based memristive devices

“…If the switching in these heterostructures was dominated by the inserted retention-stabilization layer, however, we would expect a different shape or even the opposite switching direction, as was demonstrated before for resistive switching in Al 2 O 3 (ref. 55 ). Instead, we observed that the shape and polarity of the I – V characteristics as well as the absolute voltages and currents, which are typically observed in these heterostructures, were still the same as for SrTiO 3 thin-film devices ( Supplementary Fig.…”

“…By purely empirical studies and without paying special attention to oxygen transport properties of the materials under consideration, several groups already observed improved device performance in memristive devices with inserted Al 2 O 3 layers, such as improved uniformity of HfO x - and TaO x -based devices 59 60 , improved memory windows in TiO x -based devices 55 and improved retention in GdO x -based devices 61 . On the basis of these observations, it can be assumed that our concept of the rationally designed retention-stabilization layer can be extrapolated from our model system to technologically more relevant systems.…”

Memristive Anodic Oxides: Production, Properties and Applications in Neuromorphic Computing

“…The possibility of applying multiple coating steps also opens the way to sol-gel processed double-layer structures [69], which brings potential benefits that span from increased endurance to reduced power consumption [44,[70][71][72]. For instance, in TiO 2 -based memristors oxygen vacancies migration can lead to oxygen gas evolution at the anode, which irreversibly compromises the oxide stoichiometry: the presence of a blocking layer can act as sink of oxygen ions and limit currents involved, avoiding oxide breakdown [3,73,74].…”