Reduction of plasma-induced gate oxide damage using low-energy large-mass ion bombardment in gate-metal sputtering deposition

The effects of ion species in the sputter deposition process on gate oxide reliability have been experimentally investigated. The use of xenon (Xe) plasma instead of argon (Ar) plasma in tantalum (Ta) film sputter deposition for gate electrode formation makes it possible to improve the gate oxide reliability. The Xe plasma process exhibits 1.5 times higher breakdown field and 5 times higher 50%-charge-to-breakdown (Q/sub BD/). In the gate-metal sputter deposition process, the physical bombardment of energetic ions causes generation of hole traps in the gate oxide, resulting in lower gate oxide reliability. A simplified model providing a better understanding of the empirical relationship between the gate oxide damage and the ion bombardment energy in the gate-metal sputter deposition process is also presented.