Effectiveness of Nitride Diffusion Barriers in a Self-Encapsulated Copper-Based Metallization.

Abstract

ABSTRACTCu(Ti 27 at. %) and Cu(Cr 26 at. %) codeposited on silicon dioxide substrates were annealed in a flowing NH3 ambient at 400 - 600°C for 30 min. The Ti segregates to both the surface to form a TiN(O) layer and to the alloy/SiO2 interface to form a Ti-oxide/Ti-silicide bilayer. The Cr seems to migrate only to the free surface to form a CrNx layer. A 45 nm - thick Al film was deposited after nitridation, whereupon a second anneal was performed to evaluate these nitride layers as diffusion barriers. It was found that the Ti-nitride was stable up to 500°C as compared to Cr-nitride at 600°C.