Formation of Low-Resistivity Nickel Silicide with High Temperature Stability from Atomic-Layer-Deposited Nickel Thin Film

Nickel silicide (NiSi) was formed by annealing a uniform low-resistivity nickel (Ni) film deposited by atomic layer deposition (ALD). A Ni film as-deposited at 220 °C exhibited the lowest sheet resistance of 18 Ω/sq. comparable to that of the film obtained by physical vapor deposition, even though it contained a significant amount of carbon from the metalorganic precursor. It is believed that the carbon is uniformly distributed in the film by partly forming a weak Ni 3 C phase which eliminates other crystalline defects in the film and hence lowers the resistance of the film. However, the carbon was not observed at the Ni/Si interface and in the silicon bulk except at the film surface after the annealing to form silicide. The existence of carbon at the surface of the film causes the film to maintain a low-resistivity NiSi phase up to 800 °C, without the carbon at the surface, the phase of film is changed to the high-resistivity nickel disilicide (NiSi 2 ) at such a high temperature. The deposition of Ni by ALD and the formation of low-resistivity NiSi with an increased temperature stability can be useful in fabricating advanced devices, such as nanometer scale complementally metal–oxide silicons (CMOSs) or three-dimensional (3-D) MOS devices like Fin-type field-effect transistors (Fin-FETs).