Thermal and Plasma Enhanced Atomic Layer Deposition Ruthenium and Electrical Characterization as a Metal Electrode, Sang-Joon Park , Woo-Hee Kim, Han-Bo-Ram Lee, W. J. Maeng, and H. Kim, Microelectronic Engineering, 2008
http://dx.doi.org/10.1016/j.mee.2007.01.239
Abstract
Ruthenium thin films were grown by thermal and plasma-enhanced atomic layer deposition (PE-ALD) using O2 and ammonia (NH3) plasma, respectively. RuCp2 and Ru(EtCp)2 were used as Ru precursors. Pure and low resistivity (<20 lX 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 con- trast to thermal ALD Ru. And the root-mean-square (RMS) roughness of PE-ALD Ru was lower than that of thermal ALD Ru. Addi- tionally, 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 (VFB) shift to negative value were observed. This result indicates that ALD process produces more reliable, damage free Ru gate compared to sputtering process.
