Improved Thermal Stability of NiSi Nanolayer in Ni-Si Co-sputtered Structure

Electrical, structural and morphological properties of Ni silicide films formed in Ni(Pt 4at.%)/Si(100) and Ni0.6Si0.4(Pt4at.%)/Si(100) structures at various annealing temperatures ranging from 200 to 1000 oC were studied. The Ni(Pt) and Ni0.6Si0.4(Pt) films with thickness of 15 and 25 nm were deposited by RF magnetron co-sputtering method, respectively. The annealing process of the structures was performed by using a long time annealing (LTA) procedure for 30 min. The samples were analyzed by four point probe sheet resistance (Rs) measurement, x-ray diffraction (XRD) and atomic force microscopy (AFM) techniques. It was found that the thermal stability as well as the surface morphology of “as-formed” Ni silicide nanolayers depends on annealing temperature. Ni silicide nanolayers formed in the Ni0.6Si0.4(Pt)/Si systems are more thermally stable as compared to those formed in the Ni(Pt)/Si systems during LTA procedure. It was also determined that the NiSi phase with Rs value of about 4 Ω/□ is formed in a wide temperature range from 400 to 900 oC. Indeed, the addition of Si during the Ni deposition restricts the agglomeration of NiSi layer and retards phase formation of NiSi2. According to AFM morphological analysis, NiSi layers formed in the Ni0.6Si0.4(Pt)/Si systems at high temperatures have low average surface roughness and can be used as a contact material in nanometric scale.