Pure-silica LTA, CHA, STT, ITW, and -SVR thin films and powders for low-k applications

The fluoride-mediated synthesis of pure-silica zeolite thin films with the STT and SSZ-74 (-SVR) topologies on surface-modified (1 0 0) Si wafers is reported. The films are prepared using the vapor phase transport of the fluoride mineralizing agent, a method used previously to synthesize thin films of the pure-silica zeolite topologies LTA, CHA, and ITW. The STT and -SVR films are polycrystalline, intergrown, continuous, and well-adhered to their substrates. The films are characterized by a combination of techniques, including X-ray diffraction and field emission scanning electron microscopy. The LTA, STT, -SVR, CHA, and ITW powders and films are investigated for low dielectric constant (low-k) material applications. The films are evaluated via parallel-plate capacitance measurements using an LCR meter; however, consistent k-values are not obtained due to variable film thicknesses and imperfectly parallel metal-insulator-metal structures. This variability is a limitation of the mechanical polishing equipment available, rather than the films themselves. Using a Time-Domain Reflectometer, combined with a transmission line, at various frequencies, the k-values of the powdered zeolites are determined. All the zeolites investigated, except STT, give k-values lower than those predicted from their structures using the Bruggeman effective medium model that has been commonly employed and found able to predict dielectric constants for amorphous silicas. (C) 2009 Elsevier Inc. All rights reserved.