A low power non-volatile memory element based on copper in deposited silicon oxide

We describe the electrical characteristics of W-(Cu/SiO₂)-Cu switching elements formed by thermal diffusion of copper into deposited silicon oxide. These devices switch via the electrochemical formation of a conducting filament within the high resistance Cu/SiO₂ electrolyte film. Unwritten and fully-erased devices of 350 nm to 1 μm in diameter transitioned from a high resistance state in excess of 100 MΩ to their on state at 1.3 V or less, and the erase was initiated below -0.5V. The on resistance was a function of programming current and a range of approximately 2 MΩ to below 300 D was demonstrated. Switching was possible using 3V pulses of 1 μs duration and retention was good with no systematic upward drift evident beyond 10⁵ s for devices programmed at 10 μA and read at 300 mV. Endurance for 350 nm diameter devices was determined to be in excess of 10 ⁷ cycles.