Optical functions of low-k materials for interlayer dielectrics

The optical functions of low dielectric constant (low-k) materials have been determined using a high-precision four-zone null spectroscopic ellipsometer in the spectral range from 1.5 to 5.4 eV (230-840 nm wavelength region). The ellipsometric data were fitted simultaneously with near-normal incidence reflectivity spectra (ranging from 0.5 to 6.5 eV). A general method of simultaneous treatment of ellipsometric and reflectivity data is demonstrated on representative materials used in the semiconductor industry for interlayer dielectrics: (1) SiLK-organic dielectric resin from the Dow Chemical Company, (2) Nanoglass-nanoporous silica from the Honeywell Electronic Materials Company, and (3) tetra-ethyl-ortho-silicate (TEOS) (SiO2)-the standard dielectric material. The low-k materials (SiLK and Nanoglass) were prepared by a standard spin-coating process, while the SiO2 layer was prepared by thermal decomposition from TEOS onto single-crystal silicon wafers. (C) 2001 American Institute of Physics.