NiO resistance change memory with a novel structure for 3D integration and improved confinement of conduction path

Among the candidates for future non-volatile memory, transition metal oxide (TMO) resistance change random access memory (RRAM) has shown potential for superior scalability with relatively high speed [1, 7]. The ultimate size of a TMO RRAM cell is expected to be a few tens of nm or smaller based on the filamentary conduction model [2, 3, 4, 9]. However, due to the filamentary conduction property, it is important to confine the conduction path of the current in a TMO RRAM cell because it affects the uniformity of operating voltages and currents, as well as the distribution of the low resistance state (LRS) [8]. In this work, we fabricated and characterized nanoscale Ti-doped RRAM cell arrays with i) a conventional structure (Structure 1) where the NiO is in between two metal electrodes, and ii) a novel structure where the NiO is deposited over crossing metal lines (Structure 2) for improved confinement of the conduction path. In the new structure, the memory cells showed lower RESET currents (∼90µA), larger ON/OFF ratio and improved LRS uniformity over the conventional structure. The smallest fabricated cell size is 48 nm X 48 nm, which is one of the smallest reported among NiO memory.