The effective work function (m,eff) of TaN on Hf O2 after postmetallization annealing (PMA) was investigated using TaNHf O2 Si O2 Si as a sample structure. We found that m,eff on Hf O2 is stable at PMA temperatures of less than 600 °C and is 4.6 eV, which is approximately 0.2 eV higher than that on Si O2. In contrast, m,eff is modulated by PMA at temperatures greater than 750 °C. An analysis by x-ray photoelectron spectroscopy suggests that the increased m,eff is strongly related to Ta oxide formation near the TaNHf O2 interface. The modulation of m,eff on Hf O2 is discussed on the basis of intrinsic and extrinsic Fermi level pinning due to Ta-O bond formation at the TaNHf O2 interface.
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