The effect of plasma deposition on the electrical characteristics of Pt/HfO_x/TiN RRAM device

The electrical characteristics affected by plasma ions during resistive switching are investigated on an HfOx/TiN RRAM capacitor device. Experimental fabrications of the Pt electrode by e-beam evaporation, dc sputtering and stacked Pt electrode (evaporated first followed by sputtered deposition) are presented for discussion. The samples exhibit distinct electrical characteristics both under voltage- and current-mode measurement. The sputtered sample clearly demonstrates large-scale dispersion on high resistance values caused by sputtered ionized particle (Ar⁺) damage from the voltage-mode operation. Furthermore, intermediate resistance states and anomalous switching during high- to low-state switching by current-mode indicates that the unstable conducting filamentary paths are randomly formed. This result differs completely from that of the evaporated sample. On the stacked Pt electrode, an evaporated thin Pt layer inserted before sputtering deposition effectively reduces resistance dispersion. The external plasma damage gives clues that unreliable and unstable resistive switching characteristics can result from the sputtered damage during top electrode deposition.