Area-efficient embedded resistive RAM (ReRAM) macros using logic-process vertical-parasitic-BJT (VPBJT) switches and read-disturb-free temperature-aware current-mode read scheme

Abstract

The design of resistive RAM (ReRAM) faces two major challenges: 1) cell area versus write current requirements and 2) cell read current (I CELL) versus read disturbance. This paper proposes ReRAM macros using logic-process-based vertical parasitic-BJT (VPBJT) switches and a corresponding cell array (VPBJT-CA), resulting in a 4.5× macro density compared to conventional NMOS-switch ReRAM for given write current requirements. To overcome temperature-dependent fluctuations in the base-emitter voltage difference (VBE) of VPBJT, we propose a temperature-aware bitline (BL) voltage bias (VBL-R) (TABB) scheme to provide current-mode sensing with 4.7× larger ICELL and 1.6× faster read speeds. Test results of fabricated 0.18 μm 1 Mb and 65 nm 2 Mb VPBJT ReRAM macros confirm the efficacy of the temperature-aware VBL-R, resulting in sub-5-ns random read access times. © 1966-2012 IEEE.