Study on initial growth behavior of RuO ₂ film grown by pulsed chemical vapor deposition: Effects of substrate and reactant feeding time

This study examined the nucleation behavior of RuO ₂ films grown by pulsed chemical vapor deposition (p-CVD) using a RuO ₄ solution and a N ₂(95%)/H ₂(5%) mixed gas as the Ru precursor and reactant, respectively, on various substrates such as Pt, TiN, TiO ₂, and SiO ₂ surfaces. In addition, highly doped and nondoped Si substrates were also used to understand the influence of the electrical conductivity of a given substrate material. Contrary to the nucleation behavior of atomic layer deposited and CVD Ru or RuO ₂ using metal-organic precursors, where oxygen supplying surfaces facilitate nucleation, the nucleation in this study was enhanced by oxygen consuming substrates such as TiN and Si. This is basically due to the thermal decomposition mechanism of the RuO ₄ precursor. This precursor showed fluent nucleation properties on a Pt substrate too, which is thought to come from the catalytic activity of the surface. The electrical conductivity and ionicity of the substrate had little relevance with the nucleation characteristics of the film. The addition of a H ₂ reducing gas improved the nucleation to a certain degree, but the enhancement was not substantial. The deposited films were pure and maintained a highly uniform composition along the film thickness direction. The films were already crystallized with the rutile structure.