Multi-Level Control of Conductive Filament Evolution and Enhanced Resistance Controllability of the Cu-Cone Structure Embedded Conductive Bridge Random Access Memory

Memristor is considered as one of the key components of neuromorphic hardware aiming to overcome the limitations of classical von Neumann computers, but the continuous control of the device conduction remains a challenge. Random and stochastic dynamics of weak conducting filaments (CF) hinder the precise control of the resistance states, particularly in the conductive bridge random access memory (CBRAM). The problem of random and stochastic resistive switching of the Cu-based CBRAM is largely mitigated by inserting the Cu-cone as a cation source into the memory cell (Cu-cone device). The electric field concentrated on the Cu-cone induces stronger CF with a limited number near the tip region, making the device feature distinctive from the planar Cu CBRAM. The Cu-cone device exhibits enhanced resistance controllability attributed to the well-controlled CF, improved switching reliability improvement, and multiple intermediate resistance states. Such features are used to explore its usefulness as an artificial synapse, where fluent potentiation and depression can be achieved using voltage pulses. Further research is still required to emulate the artificial synapses fully, but the feasibility is presented in this work by exploiting the similarities between the Cu cations in the CBRAM device and the Ca2+ dynamics in a biological synapse.