Plasma-free atomic layer deposition of Ru thin films using H-2 molecules as a nonoxidizing reactant

Abstract

The ruthenium (Ru) thin films were grown by atomic layer deposition (ALD) using a sequential supply of dicarbonyl-bis(5-methyl-2,4-hexanediketonato) Ru(II) (C16H22O6Ru) and H-2 as a reactant at a substrate temperature of 250 degrees C. Deposition was possible using H-2 molecules without a plasma by increasing the chamber pressure to above 10 Torr. Specifically, high-quality Ru films with a low resistivity of similar to 40 mu Omega cm and few amount of oxygen (similar to 1.2 at. %) were obtained under a chamber pressure of 300 Torr though the oxygen was contained in the precursor. Under the optimized conditions, self-limited film growth with regard to the precursor and reactant pulsing times was confirmed under elevated chamber pressures. The ALD-Ru process proposed in this study showed one of the highest growth rates of 0.12 nm/cycle on a thermally grown SiO2 substrate, as well as a very low number of incubation cycles (approximately 12 cycles). Cross-sectional view transmission electron microscopy showed that no interfacial oxide had formed during the deposition of the ALD-Ru films on a W surface using H-2 molecules, whereas similar to 7 nm thick interfacial oxide was formed when O-2 molecules were used as a reactant. The step coverage of the ALD-Ru film onto very small-sized trenches (aspect ratio: similar to 4.5 and the top opening size of 25 nm) and holes (aspect ratio: similar to 40 and top opening size of 40 nm) was excellent (similar to 100%). (C) 2016 American Vacuum Society.