Annealing effects on the film stress and adhesion of tungsten-titanium barrier layers

Tungsten-titanium (WTi) alloys are important barrier materials in microelectronic devices. Thus the adhesion of WTi to silicate glass substrates influences the reliability of these devices. One factor that affects the adhesion of barrier layers are thermal treatments during and after fabrication. To address the impact of annealing, WTi films deposited on silicate glass substrates were subjected to different annealing treatments. The stress development in the WTi film has been monitored with wafer curvature and X-ray diffraction. Quantitative measurements of the adhesion energies were performed using scratch testing to induce interface delamination. Imaging with atomic force microscopy provided the dimensions of the buckles to quantify adhesion energies. Focused ion beam cross-sections were used to verify the failing interfaces and to inspect any deformation in the film and the substrate caused by scratch testing. It was found that as the annealing duration increased, the residual compressive stresses in the film and the adhesion energy increased.