Nickel silicide compounds investigation obtained at low and high temperatures

A Ni thin film (50 nm) was deposited on n-type Si (100) wafers and subsequently subjected to post-metallization annealing at two different ranges of temperatures: low temperature annealing, ranging from 300 to 400 degrees C, with a step of 50 degrees C and high temperature annealing ranging from 850 to 950 degrees C, with a step of 50 degrees C, respectively. All thermal processes have been performed in an inert atmosphere (Ar), to avoid Ni oxidation. In order to examine the morphology of the formed nickel silicide, scanning electron microscopy analyses have been performed both in cross section and top view mode. It was concluded that the surface of the analyzed samples becomes rougher and the nickel silicide thickness increases with the temperature annealing. Furthermore, a flatter nickel silicide/silicon interface is reported at higher temperature annealing. Additionally, X-ray diffraction and micro-Raman spectroscopy were used to obtain information about the compositional properties of the resulted nickel silicide compounds. It was demonstrated that, at low temperature annealing, the dominant phase for the nickel silicide is Ni2Si (more unreacted Ni), while at high temperature more Ni consumption is observed, the dominant phase being NiSi2.