Abstract
In this thesis, we will investigate the influence of thickness of Ge interlayer on the reaction process of Ni/Ge/Si system. We use effusion cell to deposit 12, 20, and 30nm Ge interlayer, and then deposit 30nm Ni by electron beam evaporate. During the annealing process at different temperature(500, 600, and 700℃) with different time(1~18 hr), we measure the curvature of the samples in situ. After annealing, the samples were investigated by four-point probe, X-ray diffraction(XRD), Auger Electron Spectroscopy(AES), and transmission electron microscopy(TEM) with energy dispersion spectrometer(EDX). The result shows that if the Ge interlayer is below 20 nm, the samples formed Ge (NiSi1-zGez、NiSi1-yGey)/ NiSi1-zGez（Si1-xGex、Ge）/Si (y、x>z) structure after annealing at 500℃. As the annealing time increases, the ratio of Ge in the upper layer increases. When the annealing temperature raises to 700℃, the samples’ structures change into transverse NiSi1-zGez /Si1-xGex /NiSi1-zGez sandwich structure. We speculate that this is because the Si1-xGex grain grows upwardly. The percentage of Ge in the Si1-xGex grain increases, but does not change in the NiSi1-zGez grain as the annealing time increases at 700℃. The samples’ structures are Ge、NiSi1-yGey、NiSi1-zGez/ NiSi1-zGez、Si1-xGex、Ge/NiSi2/Si after annealing at 500℃ as the Ge interlayer is 30nm. The structures transfer into transverse NiSi1-zGez or NiSi2/Si1-xGex/ NiSi1-zGez or NiSi2 sandwich structures, and a thin Si1-xGex layer forms at surface after annealing at 700℃. We speculate that it is also because the Si1-xGex grain grows upwardly. The NiSi2 grain grows but the NiSi1-zGez grain decreases when the annealing time increases. NiSi2 appears early for the samples of 30nm Ge interlayer, and doesn’t be found even the annealing condition is 700℃ for 18hrs if the samples have Ge interlayer below 20nm. This is because when the thicker Ge interlayer anneals, the diffusion of Ni will be obstructed, and Ni will form NiSi2 in the Si surface. This is very different from normal nickel silicide forming sequence. We will bring up reasonable explanations to the experiment results by using the effective heat of formation.