All-in-One Analog AI Hardware: On-Chip Training and Inference with Conductive-Metal-Oxide/HfOx ReRAM Devices

By Donato Francesco Falcone ¹, Victoria Clerico ¹, Wooseok Choi ¹, Tommaso Stecconi ¹, Folkert Horst ¹, Laura Bégon-Lours  ¹, Matteo Galetta ¹, Antonio La Porta ¹, Nikhil Garg ^2,3, Fabien Alibart ^2,3, Bert Jan Offrein ¹ and Valeria Bragaglia ¹
1 IBM Research, Switzerland
2 Université de Sherbrooke, Canada
3 Université de Lille, France

Abstract 

Analog in-memory computing is an emerging paradigm designed to efficiently accelerate deep neural network workloads. Recent advancements have focused on either inference or training acceleration. However, a unified analog in-memory technology platform–capable of on-chip training, weight retention, and long-term inference acceleration–has yet to be reported. This work presents an all-in-one analog AI accelerator, combining these capabilities to enable energy-efficient, continuously adaptable AI systems. The platform leverages an array of analog filamentary conductive-metal-oxide (CMO)/HfO_x resistive switching memory cells (ReRAM) integrated into the back-end-of-line (BEOL). The array demonstrates reliable resistive switching with voltage amplitudes below 1.5 V, compatible with advanced technology nodes. The array's multi-bit capability (over 32 stable states) and low programming noise (down to 10 nS) enable a nearly ideal weight transfer process, more than an order of magnitude better than other memristive technologies. Inference performance is validated through matrix-vector multiplication simulations on a 64 × 64 array, achieving a root-mean-square error improvement by a factor of 20 at 1 s and 3 at 10 years after programming, compared to state-of-the-art. Training accuracy closely matching the software equivalent is achieved across different datasets. The CMO/HfO_x ReRAM technology lays the foundation for efficient analog systems accelerating both inference and training in deep neural networks.

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