Preparation of Highly Porous Silica Aerogel Thin Film by Supercritical Drying

Thin film preparation of porous silica aerogel is investigated as super-low dielectric constant material for ultra-large scale integrated circuits. By using Tetramethylorthosilicate based solution mixed with Dimethyl sulphoxide, which effectively suppresses solvent evaporation, thin film is successfully formed on a wafer without cracking. After an optimization of the aging process in water vapor, the film is dried in supercritical fluids of carbon dioxide, which is free from capillary force, and a high porosity aerogel with dielectric constant as low as 1.1 is obtained. Porosity and the dielectric constant of aerogels can be controlled over a wide range by changing the time of aging.