Effects of Pore Sealing on Self-Formation of Ti-Rich Barrier Layers in Cu(Ti)/Porous-Low-k Samples

Abstract

To investigate effects of pore seals on self-formation of Ti-rich barrier layers, Cu(1 at. % Ti) alloy films were deposited on porous SiOxCyH (low-k) dielectric layers in samples with and without about 6.5-nm-thick SiCN pore seals. Self-formed Ti-rich barrier layers were formed on the porous low-k layers after annealing in Ar for 2 h at 400–600 °C. The samples without pore sealing had a rough interface, indicating that Ti atoms reacted with the porous low-k layers at the pore surfaces. In contrast, the pore-sealed samples had a smooth interface. The Ti-rich barrier layers in the samples consisted of amorphous Ti oxides. In addition, polycrystalline TiC and amorphous TiN and TiC were observed to be formed beneath the Cu(Ti) alloy films in the annealed samples without pore sealing and pore-sealed samples, respectively. Note that Ti segregation at the interface was divided into two layers, suggesting that the Ti-rich barrier layers self-formed by the reaction of Ti atoms with the pore sealing and porous low-k layers are separated. The resistivity of the pore-sealed samples was lower than that of the samples without pore sealing. This is attributed to lower residual Ti atoms in the alloy films and coarser columnar grains in the pore-sealed samples.