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More and more flexible, bendable, and stretchable sensors and displays are becoming a reality. While complex engineering and fabrication methods exist to manufacture flexible thin film systems, materials engineering through advanced metallic thin film deposition methods can also be utilized to create robust and long-lasting flexible devices. In this review, materials engineering concepts as well as electro-mechanical testing aspects will be discussed for metallic films. Through the use of residual stress, film thickness, or microstructure tailoring, all controlled by the film deposition parameters, long-lasting flexible film systems in terms of increased fracture or deformation strains, electrical or mechanical reliability, can be generated. These topics, as well as concrete examples, will be discussed. One objective of this work is to provide a toolbox with sustainable and scalable methods to create robust metal thin films for flexible, bendable, and stretchable applications. [ABSTRACT FROM AUTHOR]

Rapid progress in the reduction of substrate thickness for silicon-based microelectronics leads to a significant reduction of the device bending stiffness and the need to address its implication for the thermo-mechanical fatigue behavior of metallization layers. Results on 5 μm thick Cu films reveal a strong substrate thickness-dependent microstructural evolution. Substrates with hs = 323 and 220 µm showed that the Cu microstructure exhibits accelerated grain growth and surface roughening. Moreover, curvature-strain data indicates that Stoney's simplified curvature-stress relation is not valid for thin substrates with regard to the expected strains, but can be addressed using more sophisticated plate bending theories. [ABSTRACT FROM AUTHOR]