Experimental investigation of the reliability issue of RRAM based on high resistance stateconduction

Abstract

In this paper, reliability issues of robustHfOx-based RRAM are experimentally investigated in terms of cycling ageing, temperatureimpact and voltage acceleration. All reliability issues can be estimated by the conduction ofthe high resistance state (HRS). The conduction current of the HRS exponentiallyincreases as the square root of the applied voltage, which is well explained by‘quasi-Poole–Frenkel-type’ trap assistant tunneling. Further experiments on HRS conductionat different temperatures show that the depth of the potential well of the trap inHfOx film is about 0.31 eV. The degradation induced by the cycling ageing ispossibly ascribed to the increase of the amount of oxygen ions in theTiOx layer ofthe TiN/TiOx/HfOx/TiN device. The retention times with various stress voltages at different temperatures alsoexhibit an exponential relationship to the square root of the applied voltage, indicatingthat stress current plays a dominant role for the degradation of the HRS. Anoxygen-release model is proposed to explain the relationship of retention time to HRSconduction current.