A method to control the hydrophobicity and dielectric constant of mesoporous silica films for ultralow-k-applications is described. Several surfactants have been used as sacrificial materials in (organo)silicate matrixes, prepared from tetraethoxysilane and methyltrimethoxysilane. To elucidate the relation between the composition of the films and their structure, the synthesis, chemical composition, mechanical properties, pore structure, crystallinity, and dielectric constant of the films were investigated. The high extent to which organic groups can be incorporated in these thin films opens the possibility to obtain a fully hydrophobic surface. Further, a combination of tetraethoxysilane and methyltrimethoxysilane leads to dense matrixes. The film properties were optimized for low-A- applications by varying the processing conditions. Films containing 50-60% methyltrimethoxysilane in tetraethoxysilane and cetyl trimethylammonium bromide as a surfactant appear most attractive as a low-A- material. These films are hydrophobic, have a dense matrix, and exhibit the smallest pore sizes (∼3 nm), which may facilitate integration issues.

The control of dielectric and optical properties of ordered mesoporous organosilicate films was discussed. The composition of the annealed organosilicate films was uniform over the layer thickness according to Rutherford Backscattering (RBS) depth profiling. The analysis showed that the dielectric properties of the layers strongly depended on the degree of hydrophobicity.