Ellipsometric Porosimetry of Porous Low-k Films with Quazi-Closed Cavities

Abstract

AbstractEvaluation of quasi-closed cavities connected with air through narrow necks is discussed. These cavities behave as closed pores when they are studied by Positron Annihilation Lifetime Spectroscopy (PALS). The reason is a short lifetime of o-positronium (Ps) and energy barrier that exist for Ps diffusion from large pores (d>3 nm) to small ones (d<3 nm). It is shown that more comprehensive information can be obtained using adsorption porosimetry. Standard adsorptives used in adsorption porosimetry have infinite lifetime allowing complete penetration and filling all the cavities during the measurement. Calculation of the neck and cavity sizes is based on the theory of metastable adsorption phases developed by Derjagin, Broekhoff and de Boer (DBdB). Results of evaluation are in good agreement with data obtained by SEM and TEM.