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

A thermal metalorganic atomic layer deposition (ALD) process was developed for the in situ, sequential growth of Pt/TaN_xstacks 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 MeCpPtMe₃and O₂exposure 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.