Void nucleation in metal interconnects: Combined effects of interface flaws and crystallographic slip

Abstract

A micromechanical model of void nucleation in passivated metal interconnection lines is proposed. The model is based on the evolution of stress and strain fields in a two-dimensional model system, obtained from numerical modeling. Interface flaws in the form of debond between the metal and the surrounding dielectric are assumed to exist. A unique pattern of shear stress resolved on the slip systems in the metal line, due to the presence of pre-existing debond, is found. A dislocation slip model is constructed in accordance with the shear mode. The mechanism of crystallographic slip is such that lateral thinning of the metal line at the debond region together with the slip step produced at the edges of debond lead to a net transport of atoms away from the debond area, and a physical void is thus formed. The significance and implications of this proposed micromechanism are discussed.