Question

Describe the issues of thin film stresses.

Answer 1

The presence of stress in thin films constitutes a major concern in many technological applications as excessive residual stress levels can dramatically affect the performance, reliability, and durability of material components and devices. Worst case scenarios lead to film cracking for layers subjected to tensile stress or peeling off, buckling, or blistering in the case of compressive stress. Residual stress distributions can significantly impact the adhesion and the fracture toughness of thin films, the ductility of bulk metallic glasses (BMGs),the performance of optoelectronic and aerospace components,the thermo-mechanical behavior of stacks in through silicon via (TSV) 3D integrated devices,and the resonant frequency and lifetime of micro- and nanoelectromechanical systems (MEMSs and NEMSs) or cause the emergence of hillocks and whiskers in metal interconnects at the origin of short circuit failures.Alternately, stress can have a beneficial influence on the physical properties of thin layers and nanostructures, e.g., conductivity,dielectric permittivity, piezoelectricity, magnetic anisotropy, and magneto-elastic coupling or enhancement in charge carrier mobility in silicon-based semiconductor technology.Therefore, there is significant motivation to understand the origin of stress in thin films as it can directly affect the design, processing, and lifetime of advanced materials and components.