We have demonstrated the determining factor of effective work function in TiN/HfO 2/Al 2O 3/SiO 2 gate stack structures by photoemission spectroscopy with synchrotron radiation. Difference in depth profiles indicate that the Si layer inserted at the HfO 2/Al 2O 3 interface suppresses diffusion of Al atoms into the HfO 2 layer after annealing, resulting in keeping magnitude of the high-k/SiO 2 interface dipole. However, it is found that the increase of the effective work function cannot be explained only by the interface dipole model. We suggest that oxidation of the TiN metal electrode due to oxygen diffusion from the HfO 2 layer is one of the most important factors.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)