Novel low-k polycyanurates for integrated circuit (IC) metallization
Polycyanurate-based intermetal dielectrics with lowered relative permittivity in comparison to silicon oxide as well as good electrical, thermal and mechanical properties permitting an easy low-step processing were developed. A thin reference film with a k-value of 2.91 (at 0.1 MHz) consisting of a three-dimensional polycyanurate network was obtained by curing the fluorine containing difunctional cyanate ester monomer 2,2'-bis(4-cyanatophenyl)-1,1,1,3,3,3-hexafluoroisopropylidene (F10). By co-curing of F10 with a bulky trifunctional cyanate ester monomer the dielectric constant was increased. However, co-curing with monofunctional cyanate ester monomers reduces the dielectric constant and the lowest k-value of 2.54 (at 0.1 MHz) was found for a cyanurate copolymer with a high content of m-(trifluoromethyl)phenyl structural units. All films investigated had a leakage current less-than-or-equals, slant10?10 A/cm2 and thermal and mechanical properties suitable for industrial application. Finally, first patterning attempts showed good potential for producing Cu damascene structures. Patterning using a PECVD SiO2 hard mask with partial hard mask opening was developed using ICP etch with CHF3, CF4 and He. The achieved structures showed straight profiles and no significant defects.