Impact of moisture on charge trapping and flatband voltage in Al2O3 gate dielectric films

High permittivity gate dielectric films exhibit significant charge trapping during electrical stressing. In this letter, the impact of low temperature postmetallization anneals on charge trapping in Al2O3 films is reported; anneals were performed in vacuum and forming gas ambient. These anneals not only reduce charge trapping but also move the flatband voltage towards an ideal value that corresponds to the difference in work function. Based on these experiments, it is concluded that absorbed moisture in the films provides hydrogen that concomitantly reduces charge trapping and fixed charge densities in Al2O3 films. (C) 2002 American Institute of Physics.