Improvement of the Morphological Stability by Stacking RuO2 on Ru Thin Films with Atomic Layer Deposition

Stacked RuO2/Ru structures were produced by atomic layer deposition (ALD ) using an alternating supply of bis (ethylcyclopentadienyl) ruthenium [Ru(EtCp)(2)] and O-2 gas at a deposition temperature of 270 degrees C. The type of the deposited film, either Ru or RuO2, was controlled by the total pressure in the ALD system as well as the ratio of the adsorbed Ru ( EtCp )(2) to the partial pressure of O-2 in the following O-2 gas pulse. The resistivity of the deposited Ru and RuO2 thin films was about 15 and 70 mu Omega cm, respectively. The surface morphology of Ru films annealed in O-2 ambient was seriously degraded by surface oxidation. Moreover, RuO2 films were also agglomerated due to the residual stress releasing during the annealing process. However, a stacked RuO2/Ru structure produced using ALD maintained a smooth surface even at an annealing temperature of 800 degrees C in ambient O-2. Auger electron spectroscopy confirmed that the stacked RuO2/ Ru structure successfully blocked oxygen and silicon diffusion. Therefore, the stacked RuO2/ Ru structure produced by ALD is suitable for use as the bottom electrode material for high dielectric applications. (c) 2007 The Electrochemical Society.