BEHAVIOR OF TIN AND TI BARRIER METALS IN AL-BARRIER-AL VIA HOLE METALLIZATION

The behavior of TiN and Ti barrier metals in Al-barrier-Al via structu res was investigated. When a reactive-sputtered TiN film is deposited onto an Al-1 weight percent (w/o) Si-0.5 w/o Cu surface, AlN is formed at the TiN/Al interface due to the reaction of N2 to Al, and causes a n increase in via contact resistance. To suppress the increase in via contact resistance, it is crucial to interpose a Ti buffer layer at th e TiN/Al interface. The via contact resistance of the Al/TiN/Ti/Al str ucture increases at annealing temperatures over 450-degrees-C, since A lN is formed at both the Al/TiN and TiN/Ti/Al interfaces. The Al/TiAl via contact structure presents a specific low resistance after anneali ng above 450-degrees-C, Al3Ti is formed at both the Al/Ti and Ti/Al in terfaces. Further, the Al3Ti layer can improve the electromigration pe rformance of the interconnection which consists of a TiN/Ti/Al structu re. The electromigration performance for various via structures also w as investigated. Al/Ti/Al and Al/TiN/Ti/Al via contact structures tend to increase the chain resistance before via open failure, where the d ominant mechanism is the void formation originating from the migration of Al atoms in the vias rather than the via lift-off mode. This means that Al atoms migrate easier on a TiN layer than on a Ti layer. As a result, an Al/Ti/Al via structure is better for electromigration perfo rmance.