An evaluation of the adhesive toughness of Cu thin film on substrate

While the structural density in packaged silicon integrated circuits (ICs) is increased, some reliability issues emerge. For example electromigration damage due to high current density and high temperature, and resistance capacitance (RC) delay times resulting from increases in the resistance and the capacitance between lines have been reported as key reliability issues. Recently, the employment of Cu material, which has lower resistivity than that of aluminum, is suggested to resolve these problems. In Cu-based interconnection, the barrier metals (TlN, TaN, etc.) are generally required underneath Cu line in order to defend Cu diffusion into adjacent dielectrics and underlying silicon. However, the poor adhesion of the interface between Cu and barrier metal causes the delarnination and leads to deterioration of reliability. A quantitative evaluation of adhesion between Cu and barrier metals is urgently demanded from the reliability point of view. Recently, Kamiya et al. developed the evaluation method of adhesion of the thin film structure with energy release rate. In this study, we use Kamiya's method, and the toughness of the interface between Cu and barrier metal (TiN) is quantitatively evaluated with energy release rate, where Cu film is deposited onto Si covered with TiN film by sputter.