Nanoporous polymer film properties from Brillouin light scattering and surface acoustic wave spectroscopy

Nanoporous methylsilsesquioxane polymer films, because of their low dielectric constant, have outstanding potential for application to microelectronic interconnect. Here we show that Brillouin light scattering and surface acoustic wave spectroscopy may be applied to characterise hard-to-measure properties - density/porosity, Young's modulus - of a range of polymer films from different sources. Porosity-stiffness dependences are investigated, as well as relationship to dielectric constant. Information about pore size and Poisson's ratio may also be gained, as well as showing difficulties with nanoindentation measurements.