Probing capped and uncapped mesoporous low-dielectric constant films usingpositron annihilation lifetime spectroscopy

We have measured uncapped mesoporous low-dielectric-constant films using po sitron annihilation lifetime spectroscopy (PALS), a nondestructive techniqu e, which yields both pore-size distributions and the threshold for pore int erconnectivity. Pairs of fully cured capped and uncapped identical films, i nitially containing 5%-50% porogen additions, exhibited similar signatures in PALS, establishing a technique in which film capping is unnecessary. We also found that it was possible to distinguish between closed and percolate d pores, without film capping, by comparing lifetime spectra of a film take n using different detector configurations. Interconnected pores were observ ed in cured samples, which had greater than 20% porogen additions. (C) 2000 American Institute of Physics. [S0003- 6951(00)01242-0].