Effects of annealing on the properties of atomic layer deposited Ru thin films deposited by NH3 and H2 as reactants

Abstract

Atomic layer deposition (ALD) of Ru using a non-oxidizing reactant is indispensable considering its application as a seed layer for Cu electroplating and a bottom electrode for dynamic random access memory capacitors. In this study, ALD-Ru films were deposited using a sequential supply of dicarbonyl-bis(5-methyl-2,4-hexanediketonato) Ru(II) (C16H22O6Ru) and potential non-oxidizing reducing agents, NH3 or H2, as the reactants at a substrate temperature of 250°C, and the effects of post-annealing in a H2 ambient on the film properties were investigated. The highly conformal deposition of Ru films was possible using the present reaction scheme but its resistivity was as high as ~750μΩ-cm due to carbon incorporation into the film and the formation of an amorphous structure. Low temperature annealing at 300°C at H2 ambient after deposition was found to improve the properties significantly in terms of the resistivity, impurities contents and crystallinity. For example, the film resistivity was decreased drastically to ~40μΩ-cm with both the release of C in the film and crystallization after annealing based on secondary ion mass spectrometry and transmission electron microscopy, whereas perfect step coverage at a very small-sized dual trench (aspect ratio: ~3, the top opening size of 45nm and bottom size of 20nm) was maintained after annealing.