Synaptic Characteristics and Vector‐Matrix Multiplication Operation in Highly Uniform and Cost‐Effective Four‐Layer Vertical RRAM Array

Abstract

This study implements a highly uniform 3D vertically stack resistive random‐access memory (VRRAM) with a four‐layer contact hole structure. The fabrication process of a four‐layer VRRAM is demonstrated, and its physical and electrical properties are thoroughly examined. X‐ray photoelectron spectroscopy and transmission electron microscopy are employed to analyze the chemical distribution and physical structure of the VRRAM device. Multilevel capability, reliable endurance (>104 cycles), and retention (104 s) are successfully obtained. Synaptic memory plasticity, such as spike time‐dependent plasticity, spike rate‐dependent plasticity, excitatory post‐synaptic current, paired‐pulse facilitation, and long‐term potentiation and depression is presented. Finally, the vector‐matrix multiplication (VMM) operation is conducted on a 4 × 12 VRRAM array, according to the low resistance state ratio. It is ascertained that the accuracy drop, which can occur due to VMM error, can be limited to a decrease of less than 0.44% point. Utilizing the high‐density, multilevel, and biological characteristics of VRRAM, it is possible to implement high‐performance neuromorphic systems that require densely integrated synaptic devices.

Exploration of Analog Synaptic Plasticity and Convolutional Neural Network Simulation in Bilayer TiOxNy/SnOx Memristor for Neuromorphic Systems

“…Figure 3(d) illustrates the EPSC gain versus different pulse amplitudes, highlighting a clear upward trend. This gain, calculated as A 10 / A 1 where A 10 and A 1 represent EPSC amplitudes after the final and first pulses respectively, 57 mirrors how synaptic memory strength evolves with repeated stimuli, akin to biological memory processes. These insights emphasize the memristor's capacity to emulate biological synapse activity, where EPSC intensifies with successive pulses at diverse intervals and magnitudes (Figure 3(e)).…”