Multilayer Crossbar Array of Amorphous Metal-Oxide Semiconductor Thin Films for Neuromorphic Systems

A multilayer crossbar array has been developed using amorphous metal-oxide semiconductor (AOS) thin films and implemented into a neuromorphic system. The multilayer structure can be realized, because the AOS thin films can be deposited by a simple sputtering method without heat treatment, which does not damage the underlying structures. First, Au thin films are deposited by vapor evaporation as electrodes, an amorphous In-Ga-Zn-O (
$\alpha$
-IGZO) thin film is deposited by a sputtering method as a conductance change layer, these processes are repeated, and a multilayer crossbar array is completed, where each of the three conductance change layers is sandwiched between the electrodes. Next, the multilayer crossbar array is implemented into a neuromorphic system with modified Hebbian learning, which enables autonomous learning without control circuitry, and an associative memory function is confirmed, which guarantees the possibility of further advanced functions. These results lead to astronomical large-scale integration (LSI) of synaptic elements in neuromorphic systems in the future.