Stacked NbO_x-based selector and ZrO_x-based resistive memory for high-density crossbar array applications

Resistive random-access memory (RRAM) is a promising candidate for next-generation nonvolatile memory (NVM). Furthermore, RRAM is highly suitable for integration as a crossbar array (CBA). An RRAM-based CBA (R-CBA) shows various promising features in the fields of in-memory and neuromorphic computing. However, sneak-path current through unselected cells is a major obstacle in large-scale R-CBA development. To solve this issue, we propose a TiN/ZrO_x/NbO_x/Pt one selector-one resistor (1S1R) device structure that integrates the resistive switching and selector layer in a single stack. Material and electrical analyses were conducted to investigate the selector and resistive switching characteristics of the proposed device. The 1S1R device showed high selectivity (>5 × 10¹), low-resistance state/high-resistance state ratio (>5 × 10¹), long retention (>10⁴ s), fast switching speeds (791 ns), stable operation, and excellent cell-by-cell variation. The conduction mechanism of the device was confirmed to be Schottky emission conduction. The maximum CBA size (139 × 139) was also obtained by calculating the read voltage margin. The proposed 1S1R device is suitable for large-scale CBA implementation and next-generation NVM.