Polymer thin films (less than 20 ltm) are widely used as coatings and inter-level dielectrics in microelectronic applications. In multi-layer structures, stresses generated in the films due to interaction with adjacent layers and solvent evaporation induced shrinkage, cause the polymer chains to orient in the plane of the film resulting in anisotropic film properties. Characterization of properties in all directions is essential for accurate electrical and mechanical design and modeling.
A new technique has been developed to measure, in-situ, the through-plane (z) properties of thin polymer films. A parallel plate capacitor device and an interdigitated electrode structure were used as sensors to detect changes in dielectric constant and thickness of thin polymer films under thermal or mechanical loading. The through-plane compression modulus and coefficient of thermal expansion were calculated and results are reported for benzocyclobutene (BCB) films.