Mechanical processes of the nanoscratch test are investigated using a finite element analysis of Cu/Ta/SiO2/Si multilayer films. The calculated stress distribution at the moment of delamination suggests that delamination occurs in a small region of approximately 100 nm. The driving force for delamination is the stress concentration due to strain-incompatibility at the Cu/ Ta interface resulting from the large plastic deformation in Cu. The degree of stress concentration is found to depend on internal variables, such as plastic deformation, residual stress, and the elastic modulus, and on the magnitude of lateral force.
- Residual stress