Work function tuning of reactively sputtered HfxSiyNz metal gate electrodes for advanced CMOS technology
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The aim of this research is to study the work function (Фm) tuning of the HfxSiyNz metal films through the incorporation of nitrogen. The Hf and the Si targets were co-sputtered in nitrogen (N2) and argon (Ar) plasma at 12mTorr. The gas flow ratio, RN = N2/ (N2+Ar), was adjusted to vary the nitrogen concentration in HfSiN films. The work function (Фm) of HfSiN gate extracted from the capacitance-voltage (CV) and the internal photoemission (IPE) measurements was found to decrease (from ~ 4.64eV to ~ 4.42eV) for increasing gas flow ratios (from 10% to 30%). X-ray photoelectron spectroscopy (XPS) was used for material characterization. During XPS analysis, the nitrogen (N 1s) peak intensity was observed to increase with increasing gas flow ratios. The results indicate that adjusting the nitrogen concentration in HfSiN films can be used to tune the HfSiN gate work function over ~ 0.2 eV tuning window.