A study was conducted to demonstrate that spin-on Silicalite-1 low-k films possess 0.55 nm Silicalite-1 micropores, and embedded voids of 2-5 nm and larger cavities in the range of tens of nanometers. The formation of cavities in the film occurs provided the content of residual silica from the synthesis does not suffice to fill the voids left between nanocrystals measuring 40-70nm. The higher the nanocrystal content of the suspension employed for spin-on, the larger the amount of embedded large voids. The experiment shows that spin-on Silicalite-1 films with k values below 3 contain a population of pores in the range of few tens of nanometers. The difficulty of sealing these wide voids represents a considerable and exciting challenge in the implementation of spin-on Silicalite-1 films as low-k dielectrics. The study concluded that the same properties are characteristic of other spin-on zeolite low-k films produced from zeolite nanocrstals dispersed in a precursor silica material.