Ultra-large resistance ratio of silver programmable metallization cell with stacked silicon oxide films

Characteristics of silver programmable metallization cells (Ag-PMCs) with single and stacked silicon oxide (SiOx) films were investigated. The oxygen to silicon intensity ratio of chemically-deposited SiOx and thermally-grown SiO2 films was analyzed by the energy dispersive X-ray spectroscopy (EDS). Though the set and reset voltages of Ag-PMCs with stacked SiOx films were increased owing to the high stoichiometry of thermally-grown SiO2 layer, the resistance ratio of more than 106 can be realized by the thick Ag conductive filament (CF) for the low resistance value at low resistance state (LRS). The thermally-grown SiO2 film can also prevent the regeneration of Ag-CF during retention test, leading to the superior retention properties for more than 104 s. The Ag-PMCs with stacked SiOx films can sustain a resistance ratio of five orders of magnitude for more than 400 times stable set and reset cycling, suitable for future multi-bit/cell nonvolatile memory operation.