Work function adjustment by nitrogen incorporation in HfN_x gate electrode with post metal annealing

The work function of hafnium (Hf) was modified by nitrogen (N) in dc reactive sputtering. The resistivity of the HfNx thin film is sufficiently low up to the N2 flow ratio of 10%. In addition, the work function is tuned from conduction band (4.1 eV) to midgap (4.55 eV) with increasing N2 flow ratio. From the X-ray diffraction data, the HfN(200) peak can be observed from the samples which exceed the 8% N2 flow ratio, which is responsible for the work function increase of the HfNx film.