title: Characterization of nanoporous low-k thin films by small-angle neutron scattering contrast variation.
abstract: Small-angle neutron scattering contrast variation is applied to characterization of nanoporous low-dielectric constant (low-k) thin films. Films are exposed to saturated solvent vapor in air, whereby the pores fill with liquid by capillary condensation. The pores are filled with mixtures of hydrogen- and deuterium-containing solvents to vary the neutron contrast with the matrix (wall). The composition of the solvent mixture is systematically varied to identify a composition that minimizes the scattered intensity (contrast match point). From the contrast match point composition, film characteristics including matrix density and homogeneity are assessed. Four spin-on low-k materials including a methylsilsesquioxane, an organic polymer, a xerogel, and a hydrogensilsesquioxane are characterized by the new technique. Calculated matrix mass densities are compared to independent density measurements obtained by an established specular X-ray reflectivity technique. We find no evidence of "closed pores", defined here as pores inaccessible to the probe solvent, in any of the materials studied.
authors.affiliation: Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA. hedden@matse.psu.edu
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Hedden
authors.forename: Hae-Jeong
authors.initials: HJ
authors.lastname: Lee
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Bauer