Design of Ultra Low-Dielectric Constant Organosilicate Using Block Copolymers as Templates

A new class of organosilicate has been developed that can attain an ultra low-dielectric constant, K of less than 2.0, while exhibiting good mechanical properties. In this approach, a series of triblock polymers, poly(ethylene oxide-b-propylene oxide -b-ethylene oxide) (PEO-b-PPO-b-PPO-b-PEO), are used as sacrificial materials in silicon based spin-on matrices, such as poly (methyl silsesquioxane) (MSQ). The block polymer templates are decomposed when heated to >=400C to generate homogeneous pores in the MSQ matrices. Dielectric constants equal to or less than 2.0 have been achieved with high dielectric breakdown strength(>2MV/cm) when more than 30 wt% of triblock polymers are added to MSQ. It is found from small angle neutron scatterig (SANS) that these materials have extremely small pores, on the order of 1 nm. Specular X-ray reflectivity (SXR) measurement reveals that the density decreases from 1.3 g/cm sup 3, the density of MSQ, to 0.8-0.9 g/cm sup 3, in porous MSQ. Additionally, these low k materials exhibit strong mechanical properties. The Young's modulus is found to ~3 GPa with a dielectric constant of ~ 2.0.