Deposition of nanoporous silica thin films by sol-gel

Low dielectric constant thin film of nanoporous silica synthesized by sol-gel was deposited on Si(100) substrate by spin coating. By detecting —CH 3 substituted for —OH species, which can avoid the destruction of network, surface modification was identified by Fourier transform infrared spectroscope. The hole size was about 70-80 nm observed from scanning electron microscope. By adjusting the pH value of the sol, we found that the gel time increased with the decrease o f the pH value of the sol. When heating the modified film at different temperatu res (60-400 ℃)， we can obtain the lowest dielectric constant 2.05 at 300 ℃ .