Nucleation and chemical transformation of RuO₂ films grown on (100) Si substrates by atomic layer deposition

We describe the formation of RuO₂ thin films grown using atomic layer deposition (ALD) on (100) Si substrates from Ru(EtCp)₂ and O₂, and the subsequent influence of annealing temperature and atmosphere on the surface morphology and structure of the deposited layers. The films are characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and electron diffraction (ED). The as-deposited films consist of RuO ₂ islands. No significant changes in composition or morphology are observed following annealing in N₂ for 4 h at either 500 or 700°C. Higher temperature annealing in N₂ (820°C, 4 h) results in some modifications to the morphology and structure where ED data indicate the formation of some Ru metal. However, complete transformation from as-deposited RuO₂ to Ru metal is, obtained after annealing in forming gas (95% N₂/5% H₂) at 420°C for 5 min.