Abstract
Ruthenium thin films were grown by thermal and plasma-enhanced atomic layer deposition (PE-ALD) using O 2 and ammonia (NH 3) plasma, respectively. RuCp 2 and Ru(EtCp) 2 were used as Ru precursors. Pure and low resistivity (<20 μΩ cm) Ru films were grown by PE-ALD as well as thermal ALD. PE-ALD Ru showed no nucleation delay on various substrates including TaN x , Si, and SiO 2, 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 Ta 2O 5/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.
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