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.