Fracture Toughness Analysis of Sputtered SiNx Thin Films by Energy-Based Nanoindentation Method

Fracture of SiN x layers within a semiconductor device can cause detrimental reliability issues, and measurement of fracture toughness is key in addressing this limitation. In this study, the fracture toughness of sputtered amorphous SiN x thin film was quantitatively evaluated using an energy-based nanoindentation method. Analysis of crack morphologies as a function of maximum indentation load revealed a sequential fracture process in 970 nm-thick SiN x film, consisting of delamination, buckling, and subsequent ring crack formation. The initiation of ring crack formation induced distinct pop-in event in the load–depth curves, which corresponded to an abrupt jump in the irreversible work ( \:Wᵢᵣᵣ ​)–maximum load ( \:Pₘₐₓ ​) plot. The energy released during ring crack formation was quantified from the difference in \:Wᵢᵣᵣ with and without ring crack formation at identical maximum load. The calculated fracture toughness was in agreement with expectations with a value of \:6.83\:MPa√m , which is indicative of high reliability of the energy-based method analysis. In contrast, the 94 nm-thick SiN x film exhibited no significant interfacial delamination under increasing indentation loads. Instead, radial crack propagation through film to substrate and irregular chippings were observed, highlighting the limitations of applying the energy-based method in such thin films. This work demonstrates both the applicability and the thickness-dependent limitations of the energy-based fracture toughness measurement for thin films, providing essential insights for optimizing process parameters to ensure reliability in semiconductor devices with thin coatings.