Plasma-enhanced atomic layer deposition of nickel thin film using bis(1,4-diisopropyl-1,4-diazabutadiene)nickel

Abstract

The authors report the plasma enhanced atomic layer deposition (PEALD) of a nickel thin film using bis(1,4-diisopropyl-1,4-diazabutadiene)nickel [Ni(dpdab)2] and NH3 plasma. Ni(dpdab)2 is an oxygen-free liquid Ni precursor with a vapor pressure of 0.23 Torr at 80 °C. Ni films were deposited by alternating exposures to Ni(dpdab)2 and NH3 plasma at 125–250 °C. Ni(dpdab)2 showed the atomic layer deposition (ALD) process window between 125 and 150 °C with the ALD growth of ∼2 Å/cycle. The growth rate increased significantly above 200 °C, probably due to the thermal decomposition of the Ni precursor. The resistivity of the ALD thin film decreased with increasing radio-frequency (RF) power, and lower resistivities with high RF powers are due to the lower carbon concentration and larger grain size. The minimum resistivity of the PEALD film at 150 °C in the ALD process window was 146 μΩ cm, which is significantly higher than bulk Ni resistivity (7.0 μΩ cm) mainly due to the nitrogen content (∼13%) in the as-deposited film. For a lower nitrogen concentration, the PEALD film was annealed at 400 °C under 1 Torr of H2 for 30 min, resulting in the reduction of resistivity from 146 to 13.3 μΩ cm and removal of nitrogen impurities.