Mechanism of the Key Impact of Residual Carbon Content on the Reliability of Integrated Resistive Random Access Memory Arrays

Resistive random access memories (RRAM) require high density, low power consumption and high reliability. Systematic statistic electrical, material and theoretical studies were demonstrated in this work to point out and clarify a key impact of carbon residues on the resistive switching (RS), particularly the endurance, of the integrated HfO2-based 4 kbit RRAM array. The mechanism of the carbon atoms interacting with oxygen vacancies and serving also as filament was understood in nanoscale by performing density functional theory (DFT) calculations. Under an oxygen-deficient environment, carbon atoms tend to fill in oxygen vacancy (VO··) sites and could form conductive filaments which require higher energy to be broken compared to the original VO·· filaments. By controlling the residual carbon concentration lower than 4%, highly reliable HfO2-based integrated 4 kbit RRAM array was achieved, which is of great interest for future nonvolatile memories.