A pore growth mechanism is proposed for the description of the pore size distribution and the porosity of the low dielectric constant materials. A theoretical model is constructed to portray the evolution of pore size distribution in nanoporous silica. The applicability of the model is justified by fitting it to the experimental data reported in the literature, and the effects of the essential parameters of the model on both the pore size distribution and on the porosity of a silica film are examined. The results of numerical simulation reveal that the quality of a film can be improved by increasing the rate of production of pore seeds. In particular, the total number of pores increases with the increase in the rate of production of pore seeds, and the faster the growth rate of pore the greater the number of large pores and the larger the total number of pores produced. (C) 2004 Elsevier B.V. All rights reserved.