Growth mechanism of hot wire-assisted atomic layer deposition of nickel to achieve conformal deposition on trenches: role of physisorption and chemisorption

Abstract

Highly pure nickel thin film was deposited by hot wire-assisted atomic layer deposition (HW-ALD) from NiCp2 and NH3. Due to a lack of an evident ALD window and non-ideal ALD behavior, conformal deposition is not necessarily straightforward for HW-ALD on high aspect ratio features. We therefore studied the adsorption/desorption kinetics of the precursor using a microcavity model. At temperatures above 350 °C, thermal decomposition of the precursor on the growth surface, i.e., “chemical vapor deposition mode,” occurred leading to a hazy surface morphology and poor step coverage (SC). At temperatures below 300 °C, two deposition species, physisorbed and chemisorbed Ni precursor, were involved in the film growth, with the physisorbed precursor existing near the trench opening degraded SC. We achieved selective removal of the physisorbed precursor by extending the purge period. As a result, conformal deposition was achieved at 250 °C on narrow trenches (aspect ratio: 5), whose SC was 0.86.