Measuring In-Thickness Mechanical Properties of Sub Micron Polymer Dielectric Films

The ongoing miniaturization of microelectronics has led to low-K polymer dielectric films with a thickness of several tens of nanometers. These thin polymer films generally show time dependent material properties, that are different in lateral directions and in-thickness direction. Most techniques available for measuring the mechanical properties of thin films are only capable of obtaining the in-plane modulus. To have an in-situ measurement of the in-thickness viscoelastic modulus, a parallel plate capacitor under hydrostatic pressure is used. An interdigitated electrode is used to capture the change in dielectric constant under pressure. As a first estimation, a BCB (benzocyclobutene) film was used. The in-thickness elastic modulus and change in permittivity for a 1.3 mum thick BCB (Cyclotenetrade 4022) film sandwiched between two alumina electrodes on a silicon wafer are reported to be 4.76plusmn0.42, 3.81plusmn0.26 and 3.16plusmn0.15 GPa for 20deg;, 50 deg; and 70deg; C respectively