NOVEL TECHNIQUE FOR MEASURING THROUGH-PLANE MODULUS IN THIN POLYMER-FILMS

Polymer thin films are widely used as coatings and interlevel dielectr ics in microelectronic applications. In multilayer structures, stresse s generated in the films due to interaction with adjacent layers and s olvent evaporation induced shrinkage, cause the polymer chains to orie nt in the plane of the film resulting in anisotropic film properties. Characterization of properties in all directions is essential for accu rate electrical and mechanical design and modeling. A new technique ha s been developed to measure, in-situ, the through-plane (z) stress-str ain behavior of thin polymer films. A parallel plate capacitor device and an interdigitated electrode structure were used as sensors to dete ct changes in dielectric constant and thickness of thin polymer films under compression. Results are reported for 8-14 micrometer thick, Dow Chemical Cyclotene 3022 benzocyclobutene (BCB) films, The dielectric constant was found to change linearly with stress. Using this result, the through-plane stress-strain curve was obtained.