A combined experimental and modelling study of indentation damage test on thin-film stacked structures

• Acoustic emission event corresponds to certain damage in thin-film stacked structure.
• Locations of maximum principle and shear stresses correlate to Si damage regions.
• Fracture of mode II is the main damage mechanism in Si3N4 dielectric.
• Fracture of mixed modes I and II is the main damage mechanism at SiO2-Si interface.

A combined experimental and modelling approach is developed to study the indentation damage test on the thin-film stacked structures. The mechanical properties of the top metal layer, the intermediate dielectric layer and the Si substrate in the structures are obtained through fitting the force-displacement curves from the modelling to those experimental results. The modelling of the thin-film stacked structures under indentation loading and unloading processes is then conducted to analyse the stress field and explain their indentation damage mechanisms. It is found that during the indentation loading stage, the fracture of mode II is the main damage mechanism for the through-thickness cracks in the intermediate Si3N4-Si dielectric layer. The locations of the maximum principle stress and shear stress correspond to the Si damage regions as observed in the experiment results. During the unloading stage, the fracture of mixed modes I and II is the main damage mechanism responsible for the delamination at the intermediate SiO2 dielectric layer and Si substrate interface. This study provides an understanding of the indentation damage mechanisms of the thin-film stacked structures, where cracking normally occurs at the brittle Si substrate or/and at the intermediate layer underneath the top metal layer. The application can be found in the area of the integrated circuit (IC) packaging, where those structures represent the metallization bond pad system in an IC device.