Buckle morphology of compressed inorganic thin layers on a polymer substrate

The structural integrity of thin-film multi-layer structures that are used, e.g. in displays are of paramount importance. Layer buckling and delamination is a common interfacial failure phenomenon in these structures. In this paper plasma enhanced chemical vapor deposition has been used to grow a silicon nitride layer (Si₃N₄), 400 nm thick, on a high temperature aromatic polyester substrate spin coated with a silica-acrylate hybrid coating. Two-loading mechanisms are discussed: biaxial-compressive residual stress and uniaxial-compressive external stress. The influence of loading mechanism and level of adhesion on buckle morphology has been investigated. Telephone-cord and straight buckling are observed when the layer was under biaxial-compressive residual stress while circular buckling is observed when the layer was under additional uniaxial-compressive external stress. Oxygen plasma treatment is found to enhance buckling of the Si₃N₄ layer from the polymer substrate. The buckle width and heights are found to increase with the uniaxial-compressive external strain.