Stresses in copper blanket films and damascene lines : measurements and finite element analysis

Cu is being increasingly used as a metallization material for advanced interconnects. While the mechanical properties of thin Cu films are still far from understood, it is even more true concerning the behaviour of thin lines. In this study, we report on an in-situ X-ray diffraction investigation of stresses in damascene Cu lines during annealing. At variance with the behaviour of blanket films, 0.3 μm lines exhibit a thermo-elastic behaviour which is well reproduced by finite element calculations. The triaxial stress state in the lines may explain the lack of plasticity at reduced temperatures because different stress tensor elements make the resolved stresses cancel out.