Ta₂O_5-y-based ReRAM device with annealing-free Ag:ZrN_x-based bilayer selector device

Sneak path current suppression is indispensable for realizing resistive random-access memory-based high-density crossbar array (CBA) architectures. Therefore, we present a Pt/Ta₂O_5-y/Ta/Pt nonvolatile resistive switching (RS) device and a selector device with a Pt/Ag-doped ZrN_x/Pt configuration, representing bidirectional threshold switching (TS). The cross-sections of both devices were investigated via transmission electron microscopy, and the variation in the Ag content was examined via energy-dispersive X-ray spectroscopy. The radio frequency-sputtered RS device exhibited good switching voltage uniformity (ΔV_SET and ΔV_RESET ≈ ±0.15) and a large memory window (∼5 × 10²). The selector device was developed via co-sputtering of Ag and ZrN, and the optimized device exhibited excellent selectivity (>10⁶), a very low OFF-current (∼10⁻¹¹ A), a very short delay time (∼70 ns), and stable TS characteristics. On the basis of the optimized structure, a one-selector one-memory device was fabricated by stacking these two devices, and its performance was investigated. Equivalent circuit analysis of the proposed one-selector one-resistor (1S1R) devices in a CBA configuration was performed, and the optimal array size was estimated to demonstrate the applicability of the proposed structure. The results indicated that the maximum permissible crossbar array size of the 1S1R device with the Pt/Ag-doped ZrN_x/Pt/Ta₂O_5-y/Ta/Pt structure was 2.56 × 10¹⁴ (N², N = 1.6 × 10⁷).