Evaluation of Pore Structure in Pure Silica Zeolite MFI Low-k Thin Films Using Positronium Annihilation Lifetime Spectroscopy

The pore size and pore structure in pure silica zeolite MFI in-situ and spin-on low dielectric constant (low-k) zeolite films were characterized by positronium annihilation lifetime spectroscopy (PALS). For the micropores in the in-situ and spin-on films, the pore size obtained from the on-wafer PALS method is 0.55 ± 0.03 nm, and this is in excellent agreement with the known crystallographically determined zeolitic pore size (0.55 nm). To our knowledge this is the first comparison of a PALS thin film pore size measurement with a crystallographically defined zeolite pore size. For mesopores in the spin-on film, PALS results show that they are open/interconnected and give a pore size of 2.3−2.6 nm.