EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Mechanical failures in microelectronic devices, such as delamination and cracking, play a key role for reliability concerns in today’s Back-End-of-Line structures. During use temperature differences can cause high stresses because of the CTE mismatch of the contained mechanically highly diverse materials. These stresses can cause delamination of the interfaces, which then affects the lifetime of the electronic device. To overcome these reliability concerns, finite element simulations can be utilized for design improvements that focus on the mechanical stability. However, these simulations need parameters to describe the materials and especially the interfaces.

Many ways have been presented in literature on how to evaluate interfacial toughness parameters in Back-End-of-Line stacks. Most standardized are methods based on double cantilever beam bending and four-point bending. These methods are mostly limited to macroscopic samples and fail to describe local properties of integrated circuits. Beside the macroscopic methods there also are micromechanical testing procedures that allow to characterize the structures of integrated circuits in a more localized manner. Examples for micromechanical methods are the cross-sectional nanoindentation, FIB-prepared cantilever experiments or stressed overlayer buckling experiments. These methods are based on nanoindentation approaches and can help to gain knowledge of interfacial toughness parameters at a smaller length scale.

In this study a novel experimental approach to investigate interfacial properties is presented. For this, test structures are prepared by a Dual-Damascene process and a subsequent etch back of redundant material. These structures are then tested using a nanoindentation based experimental setup. Goal of this study is to depict the functionality of the method and describe the evaluation procedure to gain an insight into the local adhesion properties of the tested interface. The resulting interface parameters may then be used in future FEM studies for design improvements.