Structure, stresses and stress relaxation of TiN/Cu multilayer and nanocomposite coatings

Abstract

AbstractStructural evolution, residual stresses, and stress relaxation at elevated temperatures were investigated for sputtered TiN/Cu multilayer films with a bilayer thickness between 100 and 800 nm, as well as nanocomposite films with a Cu content up to 30 at.%, to illuminate the effect of adding a soft metal to a hard nitride. In the nanocomposites the Cu domain size increases with rising Cu content from 7 to 22 nm at the expense of the TiN grain size, while it is strongly related to the bilayer thickness in the multilayers at constant TiN domain size. Films were thermally cycled in vacuum from room temperature up to 650 °C. Stresses during heating are governed by thermo-elastic behaviour and at temperatures above 300 °C by plastic deformation of the Cu phase and stress relaxation of both Cu and TiN, whereas the cooling phase is determined by thermo-elasticity, plastic deformation of the Cu phase and eventually tensile crack formation.