Non-parametric statistical characterization of electrical characteristics in nanoscale conductive filament devices

Abstract

We statistically analyze 3000 data points from 174 devices, including silver, copper, nickel, and cobalt filamentary devices, as well as valence change mechanism (VCM) devices. The results show that quantum confinement effects (QCEs) appear in 26% of cobalt filament devices, 17% of copper filament devices, and 5% of VCM devices, but not in silver and nickel filament devices. Further analysis is performed on the correlation of QCEs with metal ion diffusivity in metal-filament devices and with the oxygen vacancy concentration in VCM devices. In the quasi-static process, the set/reset voltages are 0.49–2 V. Further development can achieve 0.15–1.18 V. Currently, the set/reset times reach 1–120 µs. With further development, they can reach submicrosecond timescales. The analysis indicates that rectangular pulses are optimal for write/erase operations. Current performance metrics include: write/erase pulse amplitudes of 1.5–3.7 V and 1.5–2.5 V, respectively; write/erase times of 50 µs for Ag devices and microseconds to submicroseconds for others; a read voltage of 0.1–0.2 V, corresponding to a power consumption of 6–63 µW per bit; endurance below 10⁴ cycles; and retention under 10⁴ seconds. Statistical projections indicate that future write/erase voltages could decrease to 1–3 V and 1–1.65 V, respectively, with write/erase times reaching the microsecond or submicrosecond range. The read voltage could remain at 0.1 V, with a read power consumption of 0.5–24 µW per bit. Endurance may improve to 10³–10⁶ cycles, and the retention time may extend to 10⁴–10⁵ seconds. However, read power and retention need improvement over flash memory.