Structural characteristics of ultra-low k SiO2 thin films prepared using a molecular template

Nanoporous SiO2 thin films with ultra-low dielectric constants were synthesized using a molecular template method. Uniform films with pore size between 10 and 20 nm were obtained as observed by N2 adsorption/desorption isotherms and transmission electron microscopy. Fourier transform infrared spectroscopy (FTIR) and differential thermal analysis were carried out to investigate the effect of n-hexane washing on structural properties before and after the surface modification process. The results showed that –OH bonds were substituted with –CH3 bonds in the films as a result of modification of trimethylchlorosilane (TMCS)/n-hexane solution. Four kinds of model were used to analyze the relationship between porosity and dielectric constant of the films, where the dielectric constant was determined from capacitance-voltage measurements. The investigation indicated that the corresponding relationship was in accord with that estimated by the Rayleigh model.