Thin films of barrier metals (TiN, TaN, etc.) are generally required underneath Cu line in order to obstruct Cu diffusion into adjacent dielectrics. Poor adhesion of the interface between Cu and barrier metal causes delamination 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. By applying a new technique developed recently by the authors, which can evaluate adhesion of thin film structure in terms of energy release rate, we investigated the interface toughness between the submicrometer Cu film and the barrier metal (TiN) in Cr/Cu/TiN/Si metallization