Characteristics of MOS diodes fabricated using sputter-deposited W or Cu/W films

MOS diodes were fabricated having W or Cu/W gates using sputter-deposited tungsten and copper films and a lift-off process, and were characterized, using C– V and I– V measurements, before and after thermal anneals. The oxide breakdown strength, high field conduction and charge trapping of these devices were investigated. The sputtering deposition of tungsten offers films of great purity and provides us with midgap of fairly midgap films in contrast to LPCVD-deposited tungsten, which exhibits less effective midgap behaviour, although it has better adhesion to the oxide. Moreover, tungsten provides barrier action against copper penetration. This characteristic was evaluated before and after thermal annealing of Cu/W gate diodes.