High density Ru nanocrystal deposition for nonvolatile memory applications

Arrays of Ru nanocrystals 1–4nm in diameter are deposited via a hybrid chemical vapor deposition/atomic layer deposition reaction. The nanocrystal density is found to depend sensitively on the nucleating surface. A maximum density of (7–8)×1012cm−2 is achieved on Al2O3. Incorporation of these nanocrystals in floating-gate memory cells results in C-V curves that exhibit large, counterclockwise hysteresis. Leakage current analysis reveals Coulomb blockade phenomena, Frenkel-Poole emission, and space-charge-limited conduction. This analysis allows for the determination of nanocrystal size and connectivity. Charge storage converges to approximately 50% of the maximum value after two days. The corresponding loss mechanisms are discussed.