Vertical AND-Type Flash Synaptic Cell Stack for High-Density and Reliable Binary Neural Networks

A vertical AND-type (V-AND) cell stack consisting of flash memory cells is proposed and fabricated for hardware-based binary neural networks (BNNs). Low-power operation is possible with a semicircular poly-Si channel surrounded by a single word-line. In each floor, two cells facing each other along the long axis of a single channel hole share a source/drain, greatly improving cell density and making it suitable for high-density BNNs. The fabricated V-AND flash memory cells show a high on/off current ratio (
$\gt 10^{{5}}\text {)}$
, sub-pA off current, and large dynamic range (
$\gt 10^{{4}}\text {)}$
. One-shot patterning of channel holes and isolation trenches minimizes loss of uniformity due to misalignment. The proposed BNN using synaptic properties measured from fabricated V-AND cells achieves high accuracy (87.82% for the CIFAR-10 dataset).