A novel organosiloxane-vapor-annealing method has been developed for
improving the mechanical strength of porous silica films with a low
dielectric constant. Treatment of a porous silica film with
1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) under atmospheric nitrogen
above 350 °C significantly enhanced the mechanical strength (i.e., elastic
modulus and hardness) of the film. Results of Fourier transform infrared
spectroscopy (FT-IR) and thermal desorption spectroscopy (TDS) suggested the
formation of cross-linked poly(TMCTS) network on the porous silica internal
wall surfaces by the TMCTS treatment. Such TMCTS cross-linked network is
thought to enhance the mechanical strength of the low-k film.