COPS: An Efficient and Reliability-Enhanced Programming Scheme for Analog RRAM and On-Chip Implementation of Denoising Diffusion Probabilistic Model

Abstract

This work develops an efficient and reliability-enhanced programming scheme for analog RRAM, named Conductance and Operation-dependent Programming Scheme (COPS), which maximizes the probability of RESET as the final operation with small last conductance change (ΔG <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">last</inf> ) and further incorporates verify-delay-verify (VDV) to effectively suppress the post-programming relaxation effect of RRAM. Compared to the standard incremental step pulse programming (ISPP) scheme, COPS reduces the relative deviation (RD) of conductance drift by 38.6% at the same programming speed. Meanwhile, it reduces the programming time by up to 55.8% compared to the repeated programming (RP) with the same RD. The effectiveness of COPS is verified on different RRAM materials stacks and further validated by the on-chip classifications of handwritten digits and news articles, achieving 3~4-bit software-equivalent accuracy over 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> s. For the first time, a more drift-sensitive task, denoising diffusion probabilistic model (DDPM), is further implemented on-chip, yielding results comparable to 4-bit software accuracy.