Effects of annealing on the properties of atomic layer deposited Ru thin films deposited by NH3 and H-2 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 H-2, as the reactants at a substrate temperature of 250 degrees C, and the effects of post-annealing in a H-2 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 similar to 750 mu Omega-cm due to carbon incorporation into the film and the formation of an amorphous structure. Low temperature annealing at 300 degrees C at H-2 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 similar to 40 mu Omega-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: similar to 3, the top opening size of 45 nm and bottom size of 20 nm) was maintained after annealing. (C) 2016 Elsevier B.V. All rights reserved.