AVS 49th International Symposium
    Dielectrics Thursday Sessions
       Session DI+EL-ThA

Paper DI+EL-ThA10
Nanoporous MSSQ Films Characterised by Surface Acoustic Wave Spectroscopy and Brillouin Light Scattering

Thursday, November 7, 2002, 5:00 pm, Room C-107

Session: Processing and Properties of Dielectric Materials
Presenter: C.M. Flannery, Colorado School of Mines
Authors: C.M. Flannery, Colorado School of Mines
T. Wittkowski, Universitaet Kaiserslautern, Germany
K. Jung, Universitaet Kaiserslautern, Germany
B. Hillebrands, Universitaet Kaiserslautern, Germany
M.R. Baklanov, IMEC, Belgium
D.C. Hurley, National Institute of Standards and Technology
Correspondent: Click to Email
Nanoporous methylsilsesquioxane films are a leading candidate for low dielectric constant (low-@kappa@.) materials for microelectronic interconnect. However, mechanical strength reduces rapidly with lower density.(increasing porosity), yet there is a lack of techniques to characterize these properties in the @kappa@~2 range. This work reports application of surface acoustic wave spectroscopy and Brillouin light scattering to characterization of the density/porosity and Young's modulus for a range of methylsilsesquioxane films from different manufacturers. Dispersion of laser-generated surface acoustic waves detected by both piezoelectric and optical methods yields density and stiffness measurements which are independently verified by specular X-ray reflectivity, ellipsometric porosimetry and Brillouin spectroscopy. Brillouin results also show that attenuation is related to pore size. Nanoindentation measurements consistently overestimate stiffness and we discuss why this is so. The behaviour of 3 sets of films show different stiffness-porosity relationships, the initially stiffer materials declining more rapidly with increasing porosity than the softer materials. This has important consequences for stiffness properties in the @kappa@<2 region.