Suppression of defect states in HfSiON gate dielectric films on n-type Ge(100) substrates

Defect states in HfO(2) and HfSiON films deposited on Ge(100) substrates were studied by spectroscopic ellipsometry (SE) and x-ray absorption spectroscopy (XAS). In addition, structural and compositional changes in these films were examined via medium energy ion scattering (MEIS). SE and XAS experiments revealed two distinct band edge defect states, located at 1.7 +/- 0.1 eV and at 2.7 +/- 0.1 below the conduction band edges of these films. The number of defect states in HfO(2) increased noticeably following postdeposition annealing (PDA), whereas in HfSiON, it showed only small increases following the same treatment. MEIS measurements showed that Ge diffusion into HfO(2) films was enhanced significantly by PDA as well; however, this effect was less pronounced in the HfSiON films. The suppression of defect state enhancement in HfSiON films was correlated with lower levels of Ge diffusion and increased structural stability with respect to HfO(2).