Neutron and x-ray measurements of pore size distributions in low-k thin films

PMSE 447

Barry J. Bauer, barry.bauer@nist.gov1, Ronald C. Hedden, hedden@matse.psu.edu2, Michael S. Silverstein,, Hae-Jeong Lee, hae-jeong.lee@nist.gov1, Christopher L. Soles, csoles@nist.gov1, Da-Wei Liu, da-wei.liu@nist.gov1, Eric K. Lin, eric.lin@nist.gov1, and Wen-Li Wu, wenli@nist.gov1. (1) Polymers Division, National Institute of Standards and Technology, 100 Bureau Drive, stop 8541, Gaithersburg, MD 20899-8541, (2) Materials Science and Engineering Department, Penn State University, 316A Steidle, University Park, PA 16802, (3) Department of Materials Engineering, Technion - Israel Institute of Technology, Haifa, 32000, Israel
Measurement methods for porosity on a nanometer size have been developed for low dielectric constant (low-k) films deposited on silicon substrates. The volume fraction of the pores, pore size distribution (PSD), shape, connectivity, and wall density are important structural parameters that strongly affect the physical and electrical properties. Small angle neutron scattering (SANS) and x-ray reflectivity porosimetry (XRP) are combined to completely characterize the nature of the nanoporous film. SANS measures the angular dependence of scattered neutrons and models are applied to the data to extract PSD information. XRP measures the adsorption of a probe molecule as a function of pressure and PSD can be extracted by application of thermodynamic models. SANS is done on samples filled with mixtures of protonated and deuterated solvents to measure wall density and uniformity.