A-VMCO: A novel forming-free, self-rectifying, analog memory cell with low-current operation, nonfilamentary switching and excellent variability

Abstract

We demonstrate a self-rectifying, compliance-free, BEOL CMOS-compatible, resistive switching memory device, with nonfilamentary switching mechanism, forming-free operation, analog switching behavior and excellent device to device operation uniformity, down to the smallest device size. The cells have a reset switching current density of ~0.3MA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (and ~10× lower set current). This corresponds to ~5uA reset current in a 40nm-size cell, projecting down to 1uA for a 20nm-size. The switching currents are tunable by process and structural cell design. The cells can be operated with pulses as short as 10ns, at below ±7V. Cycling for at least 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cy and retention of 55°C/3yr are demonstrated, with clear paths for further improvement. These key features are enabled by the use of an amorphous-Silicon (a-Si) barrier layer, which acts as a semi-insulating oxygen scavenger in a dual-layer a-Si/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> active stack, being able to provide nonlinear IV cell characteristics, as well as to induce a large oxygen vacancy density in the switching layer.