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

Abstract

A metal–organic thermal atomic layer deposition (ALD) approach was developed for the growth of ultrathin tantalum nitride (TaNx) 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 TaNx 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%.