Study Of MOCVD TiN In Advanced Semiconductor Manufacturing

Back-end process becomes more and more important in semiconductor manufacturing industry with technical nodes scaling down. Continuous improvements are needed to reduce RC delay and power dissipation. As a diffusion barrier layer contributing to Via resistance, MOCVD (Metal-organic Chemical Vapor Deposition) TiN is one of the most important research topics. In this study, based on thin film conductivity theories, properties of TiN films on blanket film and in real devices are systematically investigated from three aspects: film thickness, impurity concentration and crystal structures. The research mainly includes crystal evolution under different plasma treatment conditions, the impact of process cycles on physical and electrical properties of TiN films, the physical and electrical behavior of TiN films in real devices and the application of ultra thin TiN films (<5nm).With N₂/H₂ plasma treatment, carbon concentration in as-deposited TiN films is greatly decreased. And the film thickness is decreased with the re-crystallization. Thus the resistivity of TiN films is remarkably reduced. It was also found that when film thickness is relatively small (<4nm in our study), although increasing process cycles gives longer plasma treatment time and results in lower carbon concentration, film resistivity is increased rather than decreased due to the extra interfaces induced by repeating cycles.In real structures, plasma treatment efficiency was found to be much higher on horizontal planes than vertical planes because of the anisotropy of plasma motion. This leads to much thicker TiN films at sidewall. With Via size decreasing, the impact of TiN films on Via resistance becomes higher. Thinner film per cycle or longer plasma treatment time is needed to relieve this impact. Finally, 2X25 process was proposed to replace the standard one to get the best integrated performance.