Characteristics of a nickel thin film and formation of nickel silicide by using remote plasma atomic layer deposition with Ni(ⁱPr-DAD)₂

Abstract

In this study, the characteristics of a thin nickel film deposited by using remote plasma atomic layer deposition (RPALD) on a p-type Si substrate and formation of nickel silicide by using rapid thermal annealing were determined. Bis(1,4-di-isopropyl-1,3-diazabutadienyl)nickel, (Ni(ⁱPr-DAD)₂) was used as the Ni precursor and an ammonia plasma was used as a reactant. This was the first attempt to deposit a thin Ni film using by Ni(ⁱPr-DAD)₂ as a precursor for the ALD process. The Ni film that was deposited by using RPALD at a growth rate of around 2.2 Å/cycle at 250°C showed a very low resistivity of 33 μΩ·cm with a total impurity concentration of around 10 at.%. The impurities in the thin film, carbon and nitrogen, were existed in the forms of C–C and C–N bonding states. The potential for removing impurities by comparing of experimental conditions, namely, the process temperature and pressure. The nitrogen impurity could be removed by using thermal desorption during each ALD cycle, and the carbon impurity could be reduced by optimizing the process pressure, which is directly related to the mean free path in the NH3 plasma. After Ni deposition, nickel silicide was formed by rapid thermal annealing (RTA) in a vacuum ambient for 1 minute. Nickel-silicide layers from obtained by used the ALD of Ni and obtained by used of the PVD Ni annealed at temperatures from 500 to 900°C. NiSi obtained by used the ALD of Ni showed better thermal stability due to the contributions of small amounts of carbon and nitrogen in the as-deposited Ni thin film. Degradation of the silicide layer was effectively suppressed by using the ALD of ALD Ni.