Channel Models and Coding Solutions for 1S1R Crossbar Resistive Memory with High Line Resistance

TL;DR

This paper models the effects of line resistance and variability in 1S1R crossbar resistive memory, proposing channel models and coding schemes to improve reliability and reduce error rates in scaled memory devices.

Contribution

It introduces BAC channel models considering line resistance and variability, and proposes coding solutions including interleaved BCH codes and location-dependent coding for enhanced reliability.

Findings

Models show non-uniform bit-error rates across arrays.

Optimized read threshold reduces raw bit-error rate.

Coding schemes significantly lower undetected error rates.

Abstract

Crossbar resistive memory with the 1 Selector 1 Resistor (1S1R) structure is attractive for nonvolatile, high-density, and low-latency storage-class memory applications. As technology scales down to the single-nm regime, the increasing resistivity of wordline/bitline becomes a limiting factor to device reliability. This paper presents write/read communication channels while considering the line resistance and device variabilities by statistically relating the degraded write/read margins and the channel parameters. Binary asymmetric channel (BAC) models are proposed for the write/read operations. Simulations based on these models suggest that the bit-error rate of devices are highly non-uniform across the memory array. These models provide quantitative tools for evaluating the trade-offs between memory reliability and design parameters, such as array size, technology nodes, and aspect ratio, and also for designing coding-theoretic solutions that would be most effective for crossbar memory. Method for optimizing the read threshold is proposed to reduce the raw bit-error rate (RBER). We propose two schemes for efficient channel coding based on Bose-Chaudhuri-Hocquenghem (BCH) codes. An interleaved coding scheme is proposed to mitigate the non-uniformity of reliability and a location dependent coding framework is proposed to leverage this non-uniformity. Both of our proposed coding schemes effectively reduce the undetected bit-error rate (UBER).