Molecular dynamics analysis of adhesion strength of interfaces between thin films

We have developed a molecular-dynamics technique for determining the adhesion strength of the interfaces between different materials. This technique evaluates the adhesion strength by calculating the adhesive fracture energy defined as the difference between the total potential energy of the material-connected state and that of the material-separated state. The extended Tersoff-type potential is applied to calculate the adhesive fracture energy of metal/dielectric interfaces as well as metal/metal interfaces. We used the technique to determine the adhesion strength of the interfaces between ULSI-interconnect materials (Al and Cu) and diffusion-barrier materials (TiN and W). It was also applied to determine the adhesion strength of interfaces between the interconnect materials and a dielectric material (SiO₂). Because the adhesion strength determined by this technique agrees well with that measured by scratch testing, this technique is considered to be effective for determining the adhesion strength.