Epoxy silsesquioxane resists for UV nanoimprint lithography

Abstract

Photopolymerizable epoxy polyhedral oligomeric silsesquioxane monomers with variable aliphatic spacer have been prepared and cured under UV radiation. Due to their organic/inorganic composition, these materials are promising candidates for microelectronic applications which requires high thermal and mechanical stabilities as well as a low dielectric constant, for example, for the fabrication of electrical interconnects. The authors pointed out by ellipsometric measurements that the use of a sensitizer in addition to the photoinitiator enhances the kinetic of the cationic polymerization of epoxy groups. The polymerization performed either in an EVG770® nanoimprint lithography stepper or under normal atmospheric conditions has been investigated by infrared spectroscopy, delivering information concerning polymerization mechanisms and allowing the optimization of the resin composition. Thermogravimetric analyses have shown that an annealing step is necessary after the UV curing of the resin to eliminate inert residues of the photoinitiator dissociation and thus improving the thermal resistance of the polymer. Finally they have demonstrated that the obtained polymers form interpenetrated networks and that their mechanical properties are retained up to a temperature of 375°C.