A 4Mb embedded SLC resistive-RAM macro with 7.2ns read-write random-access time and 160ns MLC-access capability

Abstract

Several emerging nonvolatile memories (NVMs) including phase-change RAM (PCRAM) [1-3], MRAM [4-5], and resistive RAM (RRAM) [6-8] have achieved faster operating speeds than embedded Flash. Among those emerging NVMs, RRAM has advantages in faster write time, a larger resistance-ratio (R-ratio), and smaller write power consumption. However, RRAM cells have large cross-die and within-die resistance variations (R-variations) and require low read-mode bitline (BL) bias voltage (VBL-R) to prevent read disturbance. This work proposes process/resistance variation-insensitive read schemes for embedded RRAM to achieve fast read speeds with high yields. An embedded mega-bit scale (4Mb), single-level-cell (SLC) RRAM macro with sub-8ns read-write random-access time is presented. Multi-level-cell (MLC) operation with 160ns write-ver-ify operation is demonstrated. © 2011 IEEE.