Enhanced EM endurance of TiN/AlCu/TiNx interconnection

Summary form only given. In submicron devices, TiN is used as a barrier layer in multilayered aluminum interconnection (e.g., TiN/Al/TiN). The conventional TiN layer is formed by reactive sputtering, which shows a columnar grain structure about the size of 10 nm. In this study, we focused on another technique of forming TiN from TiN_x, and compared the electromigration (EM) endurance of the multilayered interconnections using TiN_x and conventional TiN. In order to investigate the structural aspects of aluminum and the TiN formed from the TiN_x layer, the samples were prepared as follows. TiN_x film of 50 nm thickness was reactively deposited on the oxidized (400 nm thick) silicon wafer by using DC magnetron sputtering in a mixed gas atmosphere of argon and nitrogen, in which the volume percent of nitrogen was fixed at 15%. After thermal treatment at 600 °C for 20 sec using RTA, Al-0.5%Cu film (500 nm thick) and TiN (40 nm thick) film were sequentially deposited. After patterning of aluminum stripes of 0.4 μm width and 1400 μm length, the samples were alloyed at 400 °C, 30 min in 15% H₂/N ₂ ambient. Finally, a passivation layer consisting of CVD nitride (1.2 μm thick) and CVD oxide (0.4 μm thick) was deposited. The film properties before and after RTA were analyzed using RBS, XRD, and AES. Such an interconnection showed extremely high EM endurance (MTTF ~ 10⁴ min) in comparison with that using the conventional TiN as an underlying barrier layer (MTTF ~10² min). It is suggested that the crystal continuity between the Al and the TiN suppresses interface and grain boundary diffusion of Al atoms to improve the EM endurance