Atomic layer deposition for nanoscale contact applications

We review our efforts on atomic layer deposition (ALD) processes of Co and Ni thin films and their applications for nanoscale contact. First, PE-ALD Co processes was developed using various metal organic precursors and NH₃ plasma as a reactant. At optimal conditions, highly pure Co films were deposited with low resistivity down to 10 μΩcm. For this case, epitaxial CoSi₂ was formed through nitride mediated epitaxy, due the formation of a-SiN_x interlayer. The effects of nitrogen during PE-ALD Co were also studied by using N₂/H₂ plasma. To improve the conformality, thermal ALD (T-ALD) using various metal organic precursors including Co(iPr-AMD)₂ were investigated. Similarly, PE-ALD using NH₃ plasma and thermal ALD based on metal organic precursors were developed. Highly conformal Ni film was deposited and the formation of Ni silicide was studied by post-deposition annealing. The film properties were studied using various analysis techniques. Thus, ALD of transition metal is expected to be a viable process for the formation of nanoscale contact in near future device fabrication.