Novel Designs of Embedded Hybrid Cells for High Performance Memory Circuits

Abstract

Memory design has radically changed in the last few years; the emergence of new technologies has further improved performance and the traditional separation of storage levels between Static Random Access Memory (SRAM) and Dynamic Random Access Memory (DRAM) is not viable as in the past. Recently, the embedded DRAM (eDRAM) has been proposed for cache utilization to improve density while attempting to retain high performance operations; this scheme is often referred as hybrid due to the utilization of different technologies in a memory. In this paper, a hybrid scheme is proposed by adding non-volatile features and related circuits to the SRAM/eDRAM; an Oxide Resistive Random Access Memory (RRAM) is utilized as non-volatile storage in the embedded memory circuit. Different memory cells are proposed in this manuscript; they are evaluated with respect to circuit-level figures of merit as related to operational features (read, write, static noise margin, power delay product) as well as tolerance to event upsets (critical charge) and variations. Extensive simulation results using nanometric PTMs are provided. It is shown that the proposed designs offer substantial improvements over previous hybrid cells as well as a conventional NAND Flash memory cell.