Atomic layer deposition of ruthenium (Ru) thin films using ethylbenzen-cyclohexadiene Ru(0) as a seed layer for copper metallization

Abstract

Ruthenium (Ru) thin films were grown on thermally-grown SiO2 substrates using atomic layer deposition (ALD) by a sequential supply of (ethylbenzene)(1,3-cyclohexadiene)Ru(0) (EBCHDRu, C14H18Ru), and molecular oxygen (O2) at deposition temperatures ranging from 140 to 350°C. A self-limiting film growth was confirmed at the deposition temperature of 225°C and the growth rate was 0.1nm/cycle on the SiO2 substrate with a negligible number of incubation cycles (approximately 2cycles). Plan-view transmission electron microscopy analysis showed that nucleation was started after only 3 ALD cycles and the maximum nuclei density of 1.43×1012/cm2 was obtained after 5 ALD cycles. A continuous Ru film with a thickness of ~4nm was formed after 40 ALD cycles. The film resistivity was decreased with increasing deposition temperature, which was closely related to its crystallinity, microstructure, and density, and the minimum resistivity of ~14 μΩ-cm was obtained at the deposition temperature of 310°C. The step coverage was approximately 100% at trench (aspect ratio: 4.5) with the top opening size of ~25nm. Finally, the ALD-Ru film was evaluated in terms of its performance as a seed layer for Cu electroplating.