Cross-Point Resistive RAM Based on Field-Assisted Superlinear Threshold Selector

Abstract

We report a 3-D-stackable 1S1R passive cross-point resistive random access memory (RRAM). The sneak (leakage) current challenge in the cross-point RRAM integration has been overcome utilizing a field-assisted superlinear threshold selector. The selector offers high selectivity of >10 7 , sharp switching slope of <5 mV/decade, ability to tune the threshold voltage, stable operation at 125°C, and endurance of >10 11 . Furthermore, we demonstrate 1S1R integration in which the selectorsubthreshold current is <10 pA while offering >10 2 memory ON/ OFF ratio and >10 6 selectivity during cycling. Combined with self-current-controlled RRAM, the 1S1R enables high-density and high-performance memory applications.Index Terms-1S1R, cross-point memory, resistive random access memory (RRAM), select device, selectivity, sneak path.

Anatomy of Ag/Hafnia‐Based Selectors with 1010 Nonlinearity

“…By setting the read voltage (Vread) to 0.2 V and the half-read voltage (Vread/2) to 0.1 V, the 100 switching cycles in Figure 1 (b) yield a selectivity of ~10 10 in terms of the median currents at the two voltages and a maximum selectivity of 6 ×10 11 , which is the highest reported in any type of selector so far [29,30] . The turn-ON slope was <1 mV/decade, which is also the sharpest reported so far [34] .…”

“…[17] We also have recently demonstrated a highly repeatable selector based on a crested tunnel barrier with essentially unlimited endurance, [19] but the 10 5 nonlinearity obtained in these tunneling selectors may still not be sufficient for applications where ultra-large arrays are needed. Other selectors, such as mixed-ionic-electronic conduction (MIEC) [29][30][31] and FAST [29,30] have been reported with attractive performance but undisclosed materials. The concept of using engineered materials by doping fast diffusive species into dielectrics has recently been introduced [32] and demonstrated with improved nonlinearity and transition slope [33][34][35][36][37] .…”

Analogue signal and image processing with large memristor crossbars

“…Compared with passive arrays that use highly nonlinear memristors 14,[37][38][39] or discrete selector devices [40][41][42][43] to mitigate the sneak path current problem, the 1T1R scheme has a lower packing density (2.5 times the cell area). However, it allows us to independently access memristors with a linear current-voltage (I-V) relation in an array with the transistor gate control, so each memristor's conductance can be precisely tuned.…”

Resistance requirements of threshold switching selectors in 1S1R crossbar array

“…To date, selectors based on various mechanisms are proposed and mainly two kinds of I-V characteristics are observed for reported devices. Therein, Threshold switching selectors are widely concerned because of large nonlinearity and large drive current in the ON-state, including ovonic threshold switch (OTS) [4][5][6] , metalinsulator transition switch(MIT) [7,8] , field-assisted superlinear threshold switch (FAST) [9,10] and threshold vacuum switch (TVS) [11] . As figure 1, during forward voltage sweeps, it maintains high-resistive state (OFFstate) before threshold voltage (Vth) is achieved.…”