Impact of Barrier Metal Sputtering on Physical and Chemical Damages in Low-k SiOCH Films with Various Hydrocarbon Content

Abstract

Impact of barrier metal sputtering on physical and chemical damages in the low-k SiOCH films is investigated. In RF sputtering system, the potential drop across the anode sheath accelerates the ion in the plasma toward the wafer surface, inducing damages in the low-k SiOCH dielectrics. High DC bias on the target reduces the anode sheath voltage to suppress the process-induced damage in the SiOCH films. For conventional rigid and porous SiOCH films with methyl (–CH3) additives, the accelerated ions break the Si–CH3 bond, pushing up the dielectric constants. A new type of SiOCH film such as a molecular-pore-stacking (MPS) SiOCH, which is consisted of hexagonal silica ring with a large amount of hydrocarbon groups surrounding the core silica structure, exhibits high endurance to the sputtering-induced damages. The long side-chains of the hydrocarbon prevent the direct ion bonberdment to the core Si–CH3 bonds by sacrificing the C–C bond in the chains, keeping the low dielectric constant in the MPS SiOCH.