Prediction of interfacial adhesion strength of nanoscale Al/TiN films passed through patterned BEOL interconnects

The patterned layout arrangement of back-end of line (BEOL) is an important factor among reliability issues of advanced interconnects technology. BEOL determines the likelihood of interfacial fracture when adhesion between dielectric materials and conductive metals becomes poor, especially when ultra low-k dielectric is introduced into the process of semiconductor devices. Interfacial delamination of dissimilar thin films comprising multi-level interconnects increases under external loading or thermal cycling stress during device manufacturing. An Al/TiN coating underneath an ordinary pattern of BEOL interconnects is selected in this research to estimate adhesive energy by using interfacial fracture theory based on finite element analysis. By adopting the framework of four-point bending test, the proposed simulated approach was validated before comparison of the adhesion of Al/TiN stacked coatings with experimental data. Analysis indicate that increasing dielectric thickness between interfaces of Al/TiN films and Al metal line patterns from 100 nm to 600 nm induces fracture growth with crack lengths exceeding 3.5 mm. In addition, the foregoing driving force of fracture could be achieved because of Young's modulus of dielectrics, which are larger than 70 GPa.