Self-Rectifying Twin-Bit RRAM in 3-D Interweaved Cross-Point Array

A new self-rectifying twin-bit RRAM in a novel 3-D interweaved cross-point array has been proposed and demonstrated in 28-nm high-k metal gate CMOS back end of line (BEOL) process. This high density of array architecture with the cell size only 70 × 100 × 187 nm can be manufactured without additional mask or process. The RRAM film is formed by via plug over shifting between two metal lines in back-end process with TaN/TaO_xN RRAMs on both sides of a single via. The BEOL RRAM shows large read window between states. Fast switching time of 1 us for set operation and 10 us for reset was demonstrated. Excellent selectivity by its asymmetric IV characteristic enables the twin-bit 1R cells to be efficiently stacked in 3-D cross-point arrays without select transistors.