Nanoporous Ultralow Dielectric Constant Organosilicates Templated by Triblock Copolymers

Abstract

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.

Nanoporous polymeric materials: A new class of materials with enhanced properties

“…This expected reduction in the dielectric constant of nanoporous systems has been experimentally demonstrated both in polymeric materials and in other systems, such as silica [121][122][123] or organosilicates [124][125][126][127][128][129]. The results concerning the latter will be described briefly below for comparison with the results obtained in polymeric materials.…”

“…Organosilicates are also promising materials for low-k dielectrics because of their intrinsic hydrophobic behavior and the high thermal stability of the solid matrix [124][125][126][127][128][129]. Yang and coworkers [124,125] produced poly(methyl silsesquioxane) (MSQ) nanoporous organosilicate films (thicknesses of 0.3-0.8 lm) with pore sizes between 2 and 6 nm, porosities from 30% to 50%, and k values from 2 to 1.5 (lower values than that of the solid, k s % 2.8).…”

“…Yang and coworkers [124,125] produced poly(methyl silsesquioxane) (MSQ) nanoporous organosilicate films (thicknesses of 0.3-0.8 lm) with pore sizes between 2 and 6 nm, porosities from 30% to 50%, and k values from 2 to 1.5 (lower values than that of the solid, k s % 2.8). This closed-pore organosilicate exhibited good thermal stability, acceptable mechanical strength (n = 2 for the Young's modulus, and n = 3 for the hardness of the system with a porosity of 0.3), and a high electrical breakdown field (>1.5 MV/cm).…”

Advances in Ultra Low Dielectric Constant Ordered Porous Materials

“…Yang et al 46 reported a now widely accepted view that trapped water and surface hydroxyl ions. etc.…”

A Century of Dielectric Science and Technology

“…Other material formulations intentionally incorporate porosity into the material during processing. 54,55 The porous regions have a dielectric constant of 1.0, thereby lowering the overall dielectric constant of the material. Of course, the quintessential low-k material is air; as a result, studies have been undertaken that generate or incorporate air gaps between metal layers in device structures.…”