Increasing demands for faster chip speed and reduced power consumption are driving the semiconductor industry to develop insulating layers with lower dielectric constants. As the dielectric constant of a material is reduced, however, it becomes increasingly difficult to achieve the mechanical strength required to manufacture a multilevel interconnect. A new route to the synthesis of mesoporous silica has been demonstrated on 200 mm wafers. Silicate precursors dissolved in supercritical CO2 are infused into a block copolymer film. The polymer is then removed, but the resulting porous SiO2 replicates its ordered structure, enhancing the strength of the network. Incorporation of alkyl silicates further improves the film properties. Post-treatment to cap residual silanol groups renders the surface of the film hydrophobic and stabilizes it to air exposure. By appropriate choice of the block copolymer and other process parameters, the pore size and density can be varied and k values as low as 1.8 can be achieved. For a film with a dielectric constant of 2.25, the pore size is ∼4 nm. The hardness and modulus are 1.1 GPa and 7.8 GPa, respectively, as measured by nanoindentation. Four-point bend measurements yield fracture energies of 9.8 J/m2. More importantly, the film can withstand chemical mechanical planarization (CMP) using standard oxide polishing conditions.