Multilevel resistive switching behaviors of N2-plasma-treated stacked GdOx/SiNx RRAMs

Abstract

The resistive switching (RS) characteristics of N2-plasma-treated SiNx and stacked GdOx/SiNx resistance random access memories (RRAMs) have been investigated. With the N2 plasma treatment on SiNx films, the operation voltages and resistance ratio of SiNx RRAMs are significantly improved by increasing the concentration of nitrogen vacancies, leading to a reduction in the Schottky barrier height at the Ir/SiNx interface. The device reliabilities of N2-plasma-treated SiNx RRAMs such as a data retention of more than 104 s and an endurance of 100 cycles for a resistance ratio of more than two orders of magnitude are also obtained. Further, the stacked GdOx/SiNx RRAMs present multilevel RS behaviors with an unbalanced formation and rupture of the conductive filaments, resulting from the differences in dielectric permittivity and Gibbs free energy of the stacked RS materials. A resistance ratio of more than one order of magnitude between each resistance state is achieved with a stable cycling endurance and data retention testing. The Schottky emission and space-change-limited-conduction are responsible for the carrier transport mechanism of the stacked GdOx/SiNx RRAMs at a high resistance state and middle resistance state, respectively. Stacked GdOx/SiNx RRAMs with N2 plasma treatment have the potential to be adopted in future high-density nonvolatile memories.