Properties of ultrathin platinum deposited by atomic layer deposition for nanoscale copper-metallization schemes

Abstract

A thermal metalorganic atomic layer deposition (ALD) process was developed for the in situ, sequential growth of Pt/TaNx, stacks for use as barrier/seed stacks for subsequent copper electroplating. Ultrathin platinum films were deposited by alternating pulses of (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and oxygen (O2) as co-reactants. An ALD process window was established and optimized by investigating saturation of Pt film-growth rate versus MeCpPtMe3 and O2 exposure as controlled by the length of reactant pulses and the duration of the inert gas purge cycles separating the reactant pulses. The resulting low-temperature (300 °C) ALD Pt process yielded uniform and continuous Pt films with typical carbon and oxygen impurity levels around, respectively, 2.5 and 1 at.%. Film conformality was nearly 100% in 120-nm trench structures with 11:1 aspect ratio. © 2007 Materials Research Society.