A Comprehensive Study of Effect of Composition on Resistive Switching of Hf_xAl_(1-x)O_y based RRAM devices by Combinatorial Sputtering

摘要

We use the combinatorial sputter technique to simultaneously sputter HfO2 and Al2O3 targets to obtain a film of Hf_xAl_(1-x)O_y of specific compositions. The effect of oxide thickness, oxide composition (i.e. Hf:Al ratio) and oxygen gettering layer thickness on DC sweep based resistive switching performance of RRAM is investigated. The oxide thickness primarily affects forming voltage and causes the memory window to increase for the thinnest oxide (6 nm, other thicknesses - 12 nm, 18 nm). The composition of oxide has a non-linear effect on the memory window (high to low resistance ratio) and variability of resistance states whereas the variability of set voltage improves significantly for ternary oxide compared to individual binary oxides. Finally, electrode interlayer for oxygen-gettering is also critical where a thin Ti layer of 1.5nm maintains the memory window but reduces variability in HRS, LRS, reduces V_(set) and V_(reset) and improves the variability in V_(set).