Evaluation of adhesion strength of Ti films on Si(100) by the internal stress method

Abstract Titanium films were sputter deposited onto Si(100) surface. Adhesion strength of the Ti film was evaluated by the internal stress method. The Ti film was overcoated by a Ni coating in the state of a high internal stress, the value of which was about 0.5 GPa (tensile). The internal stress induces large normal and shear stress at the interface between the Ti film and the Si(100) surface. Those stresses increase with the increase of the Ni coating thickness. The stress distribution was evaluated by the finite element method. The evaluation shows that the normal stress on the interface is extremely large at the edge of the sample. This result suggests that a peeling of the Ti film is initiated at the edge and is consistent with observed spontaneous peeling phenomena. We could determine the adhesion strength of the Ti film by measuring the thickness of the Ni coating to peel off the Ti film. The value was found to range in 0.1–1 GPa region. The effect of the Ar ion bombardment of Si substrate on the adhesion enhancement was investigated in detail by this method.