On the Ni–Si phase transformation with/without native oxide

Abstract

This study has been carried out to check the effect of native oxide on the formation of Ni silicides. Ni films of various thickness were sputter deposited on Si(100) wafer without oxide, with native oxide and with oxide grown by rapid thermal oxidation, and subjected to rapid thermal annealing in nitrogen ambient for 1 min at temperatures ranging from 250 to 900°C. For the samples with native oxide, phase identification by X-ray diffraction and composition analysis by Auger electron spectroscopy showed that the Ni films do not react below 800°C. At 800 and 900°C, NiSi 2 was found to form. Cross transmission electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the layer of native oxide that caused the inhibition of Ni–Si reaction. For the Si substrate with oxide grown by rapid thermal oxidation, the formation of nickel oxide was observed. A Ni–Si–O ternary phase diagram has been constructed to interpret the results observed. The annealed unreacted Ni films show improved etch resistance and lower resistivity as compared to the as-deposited Ni film. This is attributed to the observed change in microstructure, e.g., grain growth.