Thickness-modulated optical dielectric constants and band alignments of HfO_x N_y gate dielectrics

Thickness-modulated optical dielectric constants and band alignments of HfO_x N_y films grown by sputtering have been investigated by spectroscopic ellipsometry (SE) and x-ray photoelectron spectroscopy. Based on SE measurements, it has been noted that an increase in optical dielectric constant and band gap has been observed as a function of the film thickness. Analyses of thickness-dependent band alignment of the HfO_x N _y /Si system indicate that the valence band offset increases, but only slight change in the conduction band offset, resulting from the thickness-induced change in the structure. The suitable optical dielectric constants and band offsets relative to Si make sputtering-derived HfO _x N_y film a promising candidate for high- k gate dielectrics.