Overshoot-Suppressed Memristor Crossbar Array with High Yield by AlOx Oxidation for Neuromorphic System

There is a need to design a hardware synapse array appropriate for enhancing the efficiency of neuromorphic computing systems while minimizing energy consumption. This study introduces a memristor device with an AlOx overshoot suppression layer (A-OSL) to achieve a self-compliance effect. By optimizing each cell within the 16 x 16 crossbar array, synaptic devices are successfully fabricated with reliable characteristics and 3-bit multilevel capabilities. In addition, the oxygen composition of TiOx and the annealing conditions are optimized to reduce the forming voltage and minimize the variation in the switching voltage. As a result, stable forming-free characteristics are obtained through A-OSL insertion, a reduction in forming voltage, and TiOx oxygen composition optimization. Also, target weights are accurately transferred to the A-OSL memristor crossbar array and conducted the inference process by applying spike signals to the array following the designated time step. The spiking neural network (SNN) is demonstrated by measuring vector-matrix multiplication (VMM) of the 16 x 16 crossbar array. The VMM results exhibit a classification accuracy of 90.80% for the MNIST dataset, which is close to the accuracy achieved by software-based approaches, amounting to 91.85%.