Design exploration of IGZO diode based VCMA array design for Storage Class Memory Applications

Abstract

This paper presents the Design Technology Co-optimization (DTCO) study of the 1-diode 1-Voltage controlled magnetic anisotropy (1D-1VCMA) stack, which functions as Storage Class Memory (SCM) to bridge the gap between DRAM and flash memory. The dual requirement of low sneak current and high non-linearity for bidirectional selectors in 1S-1R crossbar memories is extremely challenging to achieve practically. Moreover, the IR drop due to parasitic resistance (R-PAR) results in significant degradation in the voltage across the memory element (ME) and causes write disturbance for the 1S-1R crossbar. 1D-1VCMA solves the above-mentioned issues by having low write current (I-W), (thus reducing IR drop) and increasing the number of DINs /DOUTs to improve energy/bit. Sneak current and non-linearity are also significantly improved due of the diode selector. Based on our VCMA and IGZO diode technology data and an extensive DTCO, we are able to achieve a write energy consumption of 880fJ/bit (at a delay of 40.5ns and V-DD of 2V), and read energy consumption of 414fJ/bit (at a read delay of 39ns), thus showing a significant improvement over similar SCMs.