Nanoindentation Methodologies for Characterizing Thin (Porous) Low Dielectric Constant Materials and Copper Pads

The continuous scaling of integrated circuits and miniaturization of microelectronic devices with higher device densities to increase the performance, have led to the introduction of highly porous low dielectric constant (low-k) materials and miniature cu nails and pads. A factor that plays an increasing role in the development of these new technologies is mechanical stress. The processing, assembly and packaging of chips introduce stresses and all the building blocks should be designed and selected such that they can withstand these stresses. It is not known in detail what the strength and mechanical properties are of these small films and structures, which stresses they can survive and which parameters affect their mechanical response. Therefore, it is important to assess the mechanical properties of porous materials and Cu pads in a reliable and reproducible way. To date, nanoindentation is the most commonly used technique in the semiconductor industry to assess the mechanical properties (elastic modulus, hardness, fracture toughness and adhesion etc.) of such materials. However, special care is required when nanoindentation is performed on ultra-thin porous materials or small Cu nails or pillars since the response will be affected by the thickness, tip geometry, porosity and material/probe interactions. The focus of this PhD is to use the nanoindentation technique at its limits to understand and assess the elastic and plastic properties of porous and confined-micro size materials. Finite-element analysis is used to help getting deeper insight and fundamental understanding.

Publication year:2020

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