Selective Deposition of a Cross-Linked Low-Permittivity Polycarbosilane on Copper

Differential scanning calorimetry studies of the reaction of a cyclolinear polycarbosilane [cyclo-(CH3Si(CH2)2SiCH3)-(CH2)6]n on air-exposed Cu surfaces reveal a substantial enhancement of the cross-linking rate compared to noncatalytic surfaces, e.g., Au, Ag, Al, Si. The increased rate is attributed to surface Cu(II)-catalyzed opening of the embedded disilacyclobutane rings in the polymer. This rate enhancement is used to selectively deposit a cross-linked polycarbosilane on copper patterns in exclusion to the silicon substrate surface. These results could be attractive for realizing metal-dielectric interfaces for applications in nanodevice wiring and packaging.