Characterizing porosity in nanoporous thin films using positronium annihilation lifetime spectroscopy

Depth profiled positronium annihilation lifetime spectroscopy (PALS) is an extremely useful probe of the pore characteristics of nanoporous thin films in general and low-dielectric constant (k) thin films in particular. PALS is sensitive to all pores (both closed and open) in the size range from 0.3 to ∼300 nm and to the closed-to-open pore transition. Deduced pore sizes have been extensively compared with other techniques in an ongoing round-robin with other laboratories. The application of PALS in issues related to Cu/low-k film microchip integration will be demonstrated