Effective work function modulation of the bilayer metal gate stacks by the Hf-doped thin TiN interlayer prepared by the in-situ atomic layer doping technique

The in-situ atomic layer doping technique was used to precisely control the Hf incorporation into the thin TiN interlayer for tailoring the effective work function (EWF) of the Pt/TixHfyN bilayer metal gate stack. An analysis of the capacitance-voltage characteristics revealed the variation of the flatband voltage with the equivalent oxide thickness of the gate oxide, giving the EWF of the Pt/TixHfyN bilayer metal gate stack. Instead of the EWF (~5.7 eV) of the single-layer Pt gate electrode, the EWF of the Pt/TixHfyN bilayer metal gate stacks is tunable with the range from 4.54 eV to 5.17 eV by the insertion of the thin TiN interlayer and the Hf incorporation. The result indicates that the in-situ atomic layer doping technique is an effective approach to modulating the electrical properties of metal gate in future MOS devices.