Ultra-Scaled AlO_x Diffusion Barriers for Multibit HfO_x RRAM Operation

Abstract

For dense very large scale integration (VLSI) of high performance, multibit resistive memory (RRAM), scalability of material dimensions, as well as the operational sensitivity of the RRAM to voltage fluctuations, have to be considered. This report presents the benefits of adding 0.5-nm thick AlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> diffusion barriers at the different electrode interfaces of HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> . It is found that implementing AlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> -layers at both the bottom and the top electrode interface enables a tight control of the oxygen vacancy filament, resulting in low switching voltages and significantly improving switching endurance up to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cycles using a performance limiting resistor compliance. It is also shown that the filament in its low resistive state ( R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> LRS</sub> ) can be linearly reduced and enlarged at levels compatible to the conduction limitations of scaled selectors using an external 1T1R transistor compliance. With selector controlled resistance modulation, the R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> LRS</sub> becomes independent of the magnitude of the programming voltage and thus less sensitive to losses throughout a large memory array.