Improvement of gate oxide reliability for tantalum-gate MOS devices using xenon plasma sputtering technology

Abstract

The effects of ion species in the sputtering 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 sputtering 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 five times higher 50%-charge-to-breakdown (Q/sub BD/). In the Ta sputtering deposition process on gate oxide, the physical bombardment of energetic inert-gas ion causes the generation of hole trap sites in gate oxide, resulting in the lower gate oxide reliability. A simplified model providing a better understanding of the empirical relation between the gate oxide damage and the inert-gas ion bombardment energy in the gate-Ta sputtering deposition process is also presented.