Preparation of siloxane-silsesquioxane hybrid thin films for large-scale-integration interlayer dielectrics with excellent mechanical properties and low dielectric constants

Several kinds of homogeneous organic-inor- ganic hybrid polymer thin films were designed with im- proved mechanical properties and low dielectric constants (3.0). Novel soluble siloxane-silsesquioxane hybrid poly- mers were synthesized with cyclic and/or cage silane mono- mers, which had triorganosiloxy (R3Si1/2), diorganosiloxane (R2SiO2/2), and organosilsesquioxane (RSiO3/2) moieties with ethylene bridges at the molecular level, by the hydro- lysis and condensation of 2,4,6,8-tetramethyl-2,4,6,8-tetra(t- rimethoxysilylethyl)cyclotetrasiloxane (a cyclic monomer). The electrical properties of these films, including the dielec- tric constant (2.51), leakage current (6.4 10 11 A/cm 2 at 0.5 MV/cm), and breakdown voltage (5.4 MV/cm) were fairly good. Moreover, the mechanical properties of the hy- brid films, including the hardness (7 GPa), modulus (1.2 GPa), and crack-free thickness (2 m), were excellent in comparison with those of previous spin-on-glass materials with low dielectric constants. The excellent mechanical properties were proposed to be due to the high contents of SiOOH groups (30%) and the existence of ethylene bridge and siloxane moieties in the hybrid polymer precursors. In addition, the mechanical properties of the hybrid films were affected by the contents of the cagelike structures. The more cagelike structures a hybrid film contained, the worse its mechanical properties were. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 626 - 634, 2003