Nonvolatile Memory Characteristics with Embedded High Density Ruthenium Nanocrystals

Ruthenium (Ru) nanocrystals (NCs) embedded in SiO₂ gate stacks are formed by rapid thermal annealing for the whole gate stacks and embedded in the memory structure, which is compatible with conventional CMOS technology. The devices exhibit a substantial and clockwise hysteresis in capacitance-voltage measurement. The Ru NCs exhibit high density (2×10¹²cm^-2), small size (2-4nm) and good uniformity both in spatial distribution and morphology. The charging and long-term retention performances are explained by the Coulomb Blockade phenomena and the asymmetric electron tunnel barrier between the Ru NCs and the Si substrate, respectively.