| Nanoporous materials (NPM) are a compelling class of candidate material for future microelectronic and optoelectronics that require ultra-low dielectric constants (low-kappa) and/or refractive indices, respectively. Plasma processing of the NPM, e.g. plasma etching, is required for the anticipated technological uses.; The dielectric constants of these mesoporous silica films were measured electrically over a wide porosity range before and after sintering to investigate the effects of porosity and annealing. At porosities <40%, the dielectric constant is much higher than the predicted value. There is a significant improvement in the dielectric constants of sintered mesoporous films. The surface chemistry and thermal stability of the films was investigated.; Plasma etching of nanoporous materials is a complicated phenomenon and depends upon the overall porosity, the pore size and structure, and the concentration of organic groups on the surface of the film and inside its pores. Polymerization during fluorocarbon plasma exposure is ubiquitous and suppresses the net etching rate. A new plasma etching model that applies in the high polymerization rate regime was developed. This new model includes the effect of pore structure (pore shape and size) as well as the effect of overall porosity. According to the model, as the porosity of the film increases, surface effects become important and the etching rate is affected by both total porosity and pore geometry. The polymerization and pore sealing that occurs during fluorocarbon plasma treatment of nanoporous silica xerogel was investigated experimentally and successfully modeled using a diffusion-reaction analysis. Knudsen diffusion was assumed to be the dominant mechanism for the motion of polymer precursor species through the nanoporous material due to the pressure range of our plasma experiments. By applying a diffusion-reaction analysis with the assumptions of pore structure, model results were successfully matched with measured fluorine amounts. The model predicted the time required to reach a steady-state concentration of the polymer precursor in a pore (∼10-7sec) and predicted the time required to seal off pore necks at the surface of the dielectric (∼70 sec). |
