Preparation and properties of polysilsesquioxanes - Polysilsesquioxanes as a candidate to a low dielectrics for electronic devices

Polysilsesquioxanes PSSQ as a candidate of coatings for interlayer low dielectric films were synthesized by acid and base catalyzed hydrolytic polycondensation of RSi(OMe)(3) (R = methyl, vinyl, 3-methacryloxypropyl). Dip and spin coating of PSSQ on organic and inorganic substrates followed by curing at 100 degrees C, 400 degrees C, and 450 degrees C provided transparent and tough coating films of thickness 2000-9000 Angstrom. Polysilsesquioxanes adhered strongly to the substrates to form coating films of which the adhesion strength and hardness were 10 and 9H based on JIS K5400 comparable to ISO standard, as heating time and molecular weight increase. On curing at the elevated temperatures, they provided the films with a very smooth surface and the dielectric constants of 3.2 similar to 3.6 (R = 3-methacryloxypropyl), 3.8 similar to 4.0 (R = vinyl), and 2.5 similar to 2.7 (R = methyl) depending on film thickness and molecular weight of PSSQ. The films from PSSQ (R = methyl) were found to be porous compared with those from PSSQ (R = vinyl).