Thermal and plasma enhanced atomic layer deposition ruthenium and electrical characterization as a metal electrode

Abstract

Ruthenium thin films were grown by thermal and plasma-enhanced atomic layer deposition (PE-ALD) using 02 and ammonia (NH3) plasma, respectively. RUCp2 and Ru(EtCp)(2) were used as Ru precursors. Pure and low resistivity (<20 mu Omega cm) Ru films were grown by PE-ALD as well as thermal ALD. PE-ALD Ru showed no nucleation delay on various substrates including TaNx, Si, and SiO2, in contrast to thermal ALD Ru. And the root-mean-square (RMS) roughness of PE-ALD Ru was lower than that of thermal ALD Ru. Additionally, metal-oxide-semiconductor (MOS) capacitor composed of p-Si/ALD Ta2O5/ALD Ru (35 nm) was fabricated and C-V measurements were performed for as-deposited sample. Very small hysteresis of 20 mV was obtained, and effective work function difference to Si substrate was minimal as -0.03 V. For comparison, MOS capacitor was fabricated using sputtered Ru and large hysteresis of 0.5 V and flat band voltage (V-FB) shift to negative value were observed. This result indicates that ALD process produces more reliable, damage free Ru gate compared to sputtering process. (C) 2007 Elsevier B.V. All rights reserved.