Pure-silica zeolite thin films by vapor phase transport of fluoride for low-k applications

A new method to synthesize pure-silica zeolite films is presented. Specifically, this method uses fluoridemediated syntheses that involve the vapor phase transport of the mineralizing agent, fluoride, to crystallize a precursor film deposited by dip-coating techniques to obtain thin films of pure-silica zeolites with LTA, CHA, and ITW topologies. The films are characterized by a combination of X-ray diffraction, field emission scanning electron microscopy, and X-ray energy dispersive analyses. The films are polycrystalline, intergrown, continuous and well-adhered to their substrates. The usefulness of these thin films as low-k materials, that are needed to reduce cross-talk noise and energy dissipation between transistors in an integrated circuit, is demonstrated via evaluation of the pure-silica LTA film. The LTA topology has the lowest framework density (FD = 14.2) of the 19 known pure-silica zeolites, and theoretically could have the lowest dielectric constant. The average dielectric constants of the LTA films are calculated from capacitance measurements at a frequency of 1 MHz with metal–insulator–metal structures on lowresistivity silicon substrates, and yield an average k = 1.69, well within the ultra low-k material requirements (k between 2.3 and 2.6).