Atomic Layer Deposition of Co Using N2∕H2 Plasma as a Reactant

Cobalt thin films were deposited by plasma-enhanced atomic layer deposition (PE-ALD) using CoCp 2 as a precursor and N 2 /H 2 plasma as a reactant. We systematically investigated the changes in Co film properties depending on N 2 /H 2 gas flow ratio to study the role of N during PE-ALD Co. With increasing N 2 flow ratio, the resistivity decreased reaching minimum value at f N2/H2 = 0.25 ∼ 0.33, which corresponds to the atomic ratio in NH 3 molecule, and then increased. With only N 2 or H 2 plasma, films with very high sheet resistance over 1 M/sq were deposited. The chemical compositions of Co films were analyzed by x-ray photoelectron spectroscopy (XPS) and thickness and conformality were determined by x-ray reflectometry (XRR) and field emission scanning electron microscopy (FE-SEM), respectively. Then, the silicidation of PE-ALD Co films producing epitaxial CoSi 2 were investigated by x-ray diffraction (XRD) and high-resolution cross-sectional transmission electron microscopy (HR-XTEM).