Enhancement of CBRAM Performance by Controlled Formation of a Hourglass-Shaped Filament

In this paper, we outline the performance enhancement at low current (10 mu A) introduced by implementing CBRAM devices where the solid electrolyte is made of two layers with different Cu mobility, enabling to form a hourglass-shaped conductive filament. With such a filament configuration, the CBRAM devices combine a large memory window with high writing speed (10 ns) and a write endurance of 10(6) cycles, for an operating current of 10 mu A. We demonstrate that the filament can be reproduced by the quantum-point-contact model, revealing that the switching operation consists of the modulation of the dimensions of the filament constriction, which is continuous in both states, originating the optimal switching control at low current. The peculiar filament configuration is also proven to solve the voltage-time dilemma in this devices, enabling to combine fast low-voltage switching (3V, 10 ns) with an excellent immunity to voltage disturbs (>10 years at +/- 0.5V).