The effects of plasticity on adhesion of hard films on ductile interlayers

Adhesion measurements for thin film systems based on buckle driven delaminations, which occurred both spontaneously and induced via nanoindentation, have been used to demonstrate the effects of interlayer plasticity on film adhesion. Tungsten films deposited upon copper and tin films on semiconductor and insulator substrates show that as the hardness of the underlying copper and tin films increases the practical adhesion energy of the interface (W-Cu or W-Sn) decreases. As shear mode loading increases, this effect becomes more pronounced, while the mode I opening fracture energy remains relatively constant for a given film system. Further analysis of the copper surface after the removal of the buckled tungsten film shows a deformation induced plastic zone. The plastic zone extends beyond the original buckle and is responsible for enhancing the effective adhesion energy for these systems.