Plasma-enhanced atomic layer deposition of Co on metal surfaces

• Co films were deposited on metal surface prepared by plasma-enhanced atomic layer deposition.
• Film growth characteristics were investigated by analysis of magnetic and electrical properties of multilayer.
• The growth of PE-ALD Co is non-linearly increased with increasing number of ALD cycles.
• Growth rate at initial ALD stage depends on a substrate.
• Ta nitride interlayer was formed between Co and Ta, while a sharp interface was formed on Ru.

Co thin films were deposited using plasma-enhanced atomic layer deposition (PE-ALD) on various substrates such as Ru, Ta, SiO2, and Si. The growth characteristics of PE-ALD Co were investigated on the basis of their magnetic and electrical properties analyzed using a vibrating sample magnetometer (VSM) and four-point probe system, respectively. Compared to Co sputtering deposition, which provides a linear growth, the growth of PE-ALD Co varied on each substrate with increasing number of ALD cycles because of the surface-sensitive island growth. From the electrical properties, PE-ALD Co on a Ta substrate showed a growth mode different from those on other substrates. This difference was explained by the existence of a highly resistive interlayer, which was also directly observed via transmission electron microscopy. Since Ta was directly exposed to N2/H2 plasma during an initial island growth stage of Co, a Ta nitride interlayer was formed between Co and Ta.