Novel Selector-Induced Current-Limiting Effect through Asymmetry Control for High-Density One-Selector-One-Resistor Crossbar Arrays

Crossbar arrays that use resistance-switching random-access memory are passive arrays, requiring a high-performance cell selector. However, the array-writing margin is seriously limited by unwanted reset (switching from a low-resistance state to a high-resistance state) of the parallel connected cell to the selected cell at the moment of reset of the selected cell. This is also closely related to the presence of an interconnection-wire resistance, which induces a switching-voltage drop on the wire. Pt/TiO2/TiN selectors, with atomic-layer-deposited TiO2 films varying in thickness from 2 to 8 nm, are fabricated using a sputtered-TiN bottom-electrode layer. The selector with an 8-nm-thick TiO2 layer is found to be optimal, and is connected serially with an external cable to a Pt/2-nm-thick HfO2/TiN bipolar resistive-switching memory cell. It shows good performance without breakdown and significant switching-voltage increase without compliance current. HSPICE simulation shows that approximate to 0.5 Mb array size can be obtained by using a widely used tungsten electrode, demonstrating the feasibility of commercializing one-selector-one-resistor devices.