Atomic layer deposition of tantalum nitride for ultrathin liner applications in advanced copper metallization schemes

A metal–organic thermal atomic layer deposition (ALD) approach was developed for the growth of ultrathin tantalum nitride (TaN_x) films by alternate pulses of tert-butylimido trisdiethylamido tantalum (TBTDET) and ammonia (NH₃). An optimized ALD process window was established by investigating saturation of film-growth rate versus TBTDET and NH₃ exposures, 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 (250 °C) ALD process yielded uniform, continuous, and conformal TaN_x films with a Ta:N ratio of 1:1. Carbon and oxygen impurity levels were in the 5–8 at.% range. Associated film conformality in 100-nm trench structures with 11:1 aspect ratio was nearly 100%.