Atomic layer deposition of Ru thin film using N2/H2 plasma as a reactant

Abstract

Ruthenium (Ru) thin films were grown by atomic layer deposition using IMBCHRu [(η6-1-Isopropyl-4-MethylBenzene)(η4-CycloHexa-1,3-diene)Ruthenium(0)] as a precursor and a nitrogen–hydrogen mixture (N2/H2) plasma as a reactant, at the substrate temperature of 270°C. In the wide range of the ratios of N2 and total gas flow rates (fN2/N2+H2) from 0.12 to 0.70, pure Ru films with negligible nitrogen incorporation of 0.5at.% were obtained, with resistivities ranging from ~20 to ~30μΩcm. A growth rate of 0.057nm/cycle and negligible incubation cycle for the growth on SiO2 was observed, indicating the fast nucleation of Ru. The Ru films formed polycrystalline and columnar grain structures with a hexagonal-close-packed phase. Its resistivity was dependent on the crystallinity, which could be controlled by varying the deposition parameters such as plasma power and pulsing time. Cu was electroplated on a 10-nm-thick Ru film. Interestingly, it was found that the nitrogen could be incorporated into Ru at a higher reactant gas ratio of 0.86. The N-incorporated Ru film (~20at.% of N) formed a nanocrystalline and non-columnar grain structure with the resistivity of ~340μΩcm.