Charging characteristics of Ru nanocrystals embedded in Al2O3 matrix prepared by using the initial growth stage of Ru plasma-enhanced atomic layer deposition

Abstract

Ru nanocrystal layers were successfully prepared on the Al2O3/Si substrate by controlling the initial growth stage of Ru plasma-enhanced atomic layer deposition (PE-ALD). The spatial density and average size of the Ru nanocrystals were carefully controlled by the number of deposition cycles during the Ru PE-ALD. When the number of deposition cycles reached 60, the maximum spatial density and average diameter of Ru nanocrystals were 2.5 x 10(12) cm(-2) and 3.8 nm, respectively. In order to measure the electrical characteristics of the nanocrystal floating-gate memory, a metal oxide semiconductor (MOS) structure (p-type Si/Al2O3/Ru nanocrystal layer/Al2O3/Pt) was fabricated without breaking the vacuum. The capacitance-voltage measurement of the MOS structure revealed that the incorporation of a Ru nanocrystal layer resulted in a large flatband voltage shift (4.1 V) at a sweep range of -5 to 5 V, which corresponds to a charge spatial density of 1.22 x 10(-6) C/cm(2). Therefore, the initial stage of Ru PE-ALD can potentially be exploited for next-generation floating-gate memory cells.