Improvement of electrical properties of low dielectric constant nanoporous silica films prepared using sol-gel method with catalyst Hf

摘要

Microstructures and electrical properties of low dielectric constant (low-k) nanoporous silica films, prepared by sol-gel method using hydrofluoric acid (HF) replacing hydrochloric acid (HCl) as catalyst, have been investigated. It is found that the incorporation of HF effectively adjusts the hydrolysis and condensation of the tetraethoxylane based silica sols and makes the surface modification more sufficiently, leading to the increase of the porosity and the change in chemical bonds, and thus significantly improves the electrical properties of the films. The k value of 1.5 is reached in HF catalyzed films, which is much lower than that in HCl ones. The leakage current density are reduced to the lowest value of 6.12 x 10~(-9) A/cm~2 in HF catalyzed films. It is determined that the Schottky emission occurs in HF catalyzed films, and both Schottky and Poole-Frenkel emissions occur in HCl ones, which may be due to the lower effective oxide charge density near the nanoporous silica and Si interfaces in HF catalyzed films than in HCl ones.