Mechanical characterization of thin film materials with nanoindentation measurement and finite element analysis

MEMS (Micro-electro-mechanical systems) and NEMS (Nano-electro-mechanical systems) are composed of thin films and composite nanomaterials. Nanoindentation testing method has been successfully utilized to measure mechanical properties of materials at sub-micro and nano scales. To reduce complexity and uncertainty of nanoindentation experiments, finite element analysis (FEA) has been used to model the indentation process. Correlation of FEA results with nanoindentation measurements is expected to overcome the aforementioned obstacles and lead to accurate mechanical characterization.; A systematic method of mechanical characterization on thin films with nanoindentation measurement and FEA is provided to investigate intrinsic mechanical properties of thin films. Firstly, thin film's roughness parameters and mechanical properties, and substrate's effect on thin film's measured mechanical properties were studied with atomic force microscopy and Berkovich nanoindentation testing. Secondly, the mechanical properties of thin films were characterized with both nanoindentation measurement and FEA. It is concluded that nanoindentation measurements coupled with FEA provide accurate mechanical characterization on thin films. Moreover, utilization of infinite elements in FEA is a suitable and elegant way to account for real specimen sizes.; A film/substrate-friction-contact model was developed with FEA to study the mechanical properties of thin films at different interfacial bonding conditions and thus help better understanding of the interfacial reliability. This film/substrate-friction-contact model can be utilized for cone indenters with different half angles. In addition, this model can be utilized for the micro and macro indentations once the dimensional parameters are set correspondingly.; Lastly, mechanical responses of nanoindentation on soft film/hard substrate and hard film/soft substrate material systems were investigated with FEA. It is concluded that the calculated Young's modulus of thin films more sensitively respond to the indenter's maximum displacement than the calculated hardness; the relationship between indenter's contact depth and maximum displacement for the thin film/substrate materials deviates from the linear relationship, which accounts for their corresponding bulk materials; moreover, the piling-up of the soft film/hard substrate and sinking-in of the hard film/soft substrate are more significant than their corresponding soft bulk material and hard bulk material, respectively.