Nanoporous Ultralow Dielectric Constant Organosilicates Templated by Triblock Copolymers

Triblock polymers, poly(ethylene oxide- b -propylene oxide- b -ethylene oxide) (PEO- b -PPO- b -PEO), are used as molecular templates in poly(methyl silsesquioxane) (MSQ) matrixes to fabricate nanoporous organosilicates for low dielectric constant applications. The results show that aggregation of block copolymers in the MSQ matrix can be prevented with the fast solvent evaporation which accompanies spin casting. Solid-state NMR shows that the triblock copolymer microphase-separates from the MSQ during a curing step, resulting in polymer domain size in the range of 3−15 nm, depending upon the polymer composition and loading percentage. When the films are heated to 500 °C, extremely small pores (2−6 nm) are generated, which are studied by small angle neutron scattering and positronium annihilation lifetime spectroscopy. These materials attain ultralow dielectric constants ( k ≈ 1.5) with good electrical and mechanical properties.