Effect of Nitrogen on Band Alignment in HfSiON Gate Dielectrics

Nitridation of HfSiO films improves certain physical and electrical properties—when using gate stack layers—such as their crystallization temperature and their resistance to interdiffusion. We have studied the band alignment of HfSiO and HfSiON films by soft x-ray photoemission, oxygen K-edge x-ray absorption, and spectroscopic ellipsometry. Nitridation of HfSiO reduced the band gap by 1.50eV±0.05eV, and the valence- and conduction-band offsets by 1.2eV±0.1eV and 0.33eV±0.05eV, respectively. Although the band-gap reduction should lead to increased leakage, the barrier heights are still sufficient for proposed near-future complementary metal-oxide-semiconductor applications.