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 mum in diameter transitioned from a high resistance state in excess of 100 MOmega to their on state at 1.3 V or less, and the erase was initiated below -0.5 V. The on resistance was a function of programming current and a range of approximately 2 MOmega to below 300 Omega was demonstrated. Switching was possible using 3 V pulses of 1 mus duration and retention was good with no systematic upward drift evident beyond 105 s for devices programmed at 10 muA and read at 300 mV. Endurance for 350 nm diameter devices was determined to be in excess of 107 cycles.