An 8 Mb Multi-Layered Cross-Point ReRAM Macro With 443 MB/s Write Throughput Akifumi Kawahara, Ryotaro Azuma, Y uuichirou Ike da, Ken Kawai, Y oshikazu Katoh, Y ukio Hayakawa, Kiyotaka Tsuji, Shinichi Y oneda, Atsushi Himeno, Kaz uhiko Shimakawa, Takeshi Takagi, Takumi Mikawa, and

Abstract

An 8-Mb multi-layered cross-point resistive RAM (ReRAM) macro has been developed with 443 MB/s write throughput (64-bits parallel write per 17.2-ns cycle), which is al- most twice as fast as competing me thods. It uses th e fast switching performance of TaOx ReRAM and a new write architecture to reduce the sneak current in a cross-point cell array structure based on an 0.18-µm process. Fi rst, a bidirectional diode as a memory cell select element is developed to reduce the sneak current. Second, PMOS and NMOS are used select transistors in the source follower to realize stable switching for the selected cell in the multi-layered cross-point structure. Third, a hierarchical bitline (BL) structure is employed with a short bitline. Fourth, multi-bit write architecture is developed to realize fast write operation and to suppress the sneak current.