Effect of the residual stress on the determination through nanoindentation technique of the Young's modulus of W thin film deposit on SiO2/Si substrate

The aim of this paper is to show the decrease of the Young's modulus determined by nanoindentation technique of tungsten thin films, obtained by DC magnetron sputtering and deposited on SiO2/Si layer, with the Xenon pressure in the reactor. As tungsten is an isotropic material, this variation is attributed to high residual stresses (tensile or compressive), whose average values are determined by others experimental techniques. An inverse method coupled with a numerical indentation modelling (FEM) of tensile or compressive W thin film deposited on Si substrate ratify this interpretation and confirm the dependence of the Young's modulus determined by nanoindentation tests on the equibiaxial residual stress. Moreover, the analysis shows that the equibiaxial residual stress is not homogeneous in the film but presents a very high gradient depending on the film thickness.