The effect of sol viscosity on the sol-gel derived low density SiO2 xerogel film for intermetal dielectric application

SiO2 sol was prepared using a typical two-step acid/base catalyst procedure to investigate the effect of sol viscosity on the microstructure of SiO2 xerogel film. The viscosity of coating sol was varied in the range of 4 to 50 cP. With coating sols in the viscosity range of 10-40 cP, stable SiO2 xerogel films of 73.5-47.5% porosity could be prepared. During the spin coating of sol, high evaporation of solvent was inevitable and this induced the accelerated and abnormal gelation. The microstructure of SiO2 xerogel was found to be largely dependent on the viscosity of coating sol. Dielectric constant and leakage current density were obtained in metal-insulator-semiconductor structure. The measured dielectric constants were ranged from 1.99 to 2.45 according to the porous nature of xerogel films. Leakage current density measurements showed that at low electric field strength the conduction behavior of low density xerogel film was ohmic conduction, but at high field strength, Poole-Frenkel electron emission was the conduction mode. (C) 1998 Elsevier Science S.A. All rights reserved.