Analysis of quantum conductance, read disturb and switching statistics in HfO2 RRAM using conductive AFM

Most studies on resistance switching have been carried out at the device level with the standard electrical characterization setup, which allows for effective automated reliability test and extensive characterization of the lifetime of an RRAM device. However, it is equally important to be able to probe the switching phenomenon at the nanoscale so as to improve insight on the bias-dependent kinetic behavior of the filament during multiple reversible breakdown and recovery cycles. This study aims to do just that by probing HfO2 blanket films (~ 4 nm) with a W bottom electrode using an ultra-sharp Pt-wire conductive AFM (CAFM) tip with an areal resolution of ~10-20 nm at ambient conditions. The use of the CAFM allows for a more reliable assessment of single filament evolution behavior as possible multiple filamentation events (common at the device level) are rare for such small probing areas. The role of oxygen vacancy induced filaments is studied here by using low compliance setting and moderate voltage levels, ensuring operation in the sub-quantum conductance regime. Our results show good repeatable switching trends and also provide insight on the quantum conductance phenomenon in oxygen vacancy based filaments. The read disturb trends in switching are investigated for the high resistance state (HRS) and the impact of tip-induced mechanical stresses on forming lifetime is also presented, which could serve as a motivator for further studies on non-volatile memory (NVM) reliability for flexible electronics devices and system on chip (SoC) applications.