Kinetic study on hot-wire-assisted atomic layer deposition of nickel thin films

Abstract

High-purity Ni films were deposited using hot-wire-assisted atomic layer deposition (HW-ALD) at deposition temperatures of 175, 250, and 350 °C. Negligible amount of nitrogen or carbon contamination was detected, even though the authors used NH2 radical as the reducing agent and nickelocene as the precursor. NH2 radicals were generated by the thermal decomposition of NH3 with the assist of HW and used to reduce the adsorbed metal growth precursors. To understand and improve the deposition process, the kinetics of HW-ALD were analyzed using a Langmuir-type model. Unlike remote-plasma-enhanced atomic layer deposition, HW-ALD does not lead to plasma-induced damage. This is a significant advantage, because the authors can supply sufficient NH2 radicals to deposit high-purity metallic films by adjusting the distance between the hot wire and the substrate. NH2 radicals have a short lifetime, and it was important to use a short distance between the radical generation site and substrate. Furthermore, the impurity content of the nickel films was independent of the deposition temperature, which is evidence of the temperature-independent nature of the NH2 radical flux and the reactivity of the NH2 radicals.