Exploring Ni-Si thin-film reactions by means of simultaneous synchrotron X-Ray diffraction and substrate curvature measurements

We propose a new approach to follow stress development during solid state reaction between a Ni thin film and Si (0 0 1). Substrate curvature measurements were performed simultaneously with X-ray diffraction at LURE synchrotron radiation facility. The measured curvature yields the average force whereas X-ray diffraction yields the different phases that form as well as the strain variation undergone by these phases. During annealing with a constant heating rate of 2 deg. C/min, Ni grain growth is first observed, followed by the formation of Ni2Si, Ni3Si2 and then NiSi. The Ni2Si formation is correlated with a rapid increase in compressive force. At the end of Ni consumption, the force evolves in tension until NiSi formation, which is accompanied by an additional increase in compressive force and then a final force relaxation at higher temperature. It is interesting to note that the NiSi phase appears at the expense of Ni3Si2, and surprisingly, at the benefit of Ni2Si until the Ni3Si2 is completely consumed. Strain buildup during Ni2Si and Ni3Si2 formation exhibit clear differences. Both Ni3Si2 and Ni2Si phases exhibit a bell shape behavior of the strain evolution versus temperature at variance with predictions from the Zhang and d'Heurle model [Thin Solid Films. 213, 1992, 34]