Integration of atomic layer deposition tantalum nitride and platinum with electrochemical deposition of copper for interconnect technology.

摘要

In current copper metallization fabrication, Cu diffusion barrier and seed layer for electroplating are deposited by physical vapor deposition (PVD), which could be problematic as the feature size of the copper interconnect continuous scales down, partially due to the non-conformal deposition profile. Atomic layer deposition (ALD) provides a valid alternative by offering excellent conformality, uniformity, accurate film thickness control, and other advantages.;The research work was focused on processes developments and integration of two ALD processes with electrochemical deposition (ECD) Cu for advanced interconnect application. Firstly, a thermal ALD tantalum nitride process was developed for diffusion barrier applications using tertbutylimidotris(diethylamido)tantalum (TBTDET) and ammonia (NH3), the conformality, composition and structure of the resulting TaNx films were investigated. Secondly, the diffusion barrier performance of the ALD TaNx was examined under thermal stress as well as a combination of thermal and electrical stress. ALD TaN, PVD TaN, and PVD Ta were compared as liner material, when integrating with PVD Cu and mechanical polish to fabricated Cu wire test structure. The effective resistivity of Cu lines was documented for different liner deposition techniques and materials. Thirdly, a thermal ALD platinum process was developed for Cu electroplating seed layer using (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and oxygen (O2). Again, the investigation focused on the resulting film properties: thickness, composition, structure, and resistivity etc. Finally, the feasibility of Cu electroplating on ALD TaN/Pt stack was tested. The nucleation of ECD Cu on ALD Pt and PVD Cu seed layer and the resulting Cu film structure were compared. Thermal stability of ECD Cu on ALD Pt was examined. The integration of an all ALD liner/seed layer with ECD Cu was demonstrated to fill the trenches structure.