Mechanism for Fermi Level Pinning at Electrode/Hf-Based Dielectric Interface: Systematic Study of Dependence of Effective Work Functions for Polycrystalline Silicon and Fully Silicided NiSi Electrodes on Hf Density at Interface

We systematically investigated the dependence of the effective work functions (Φeff) for polycrystalline silicon (poly-Si) and fully silicided NiSi electrodes on Hf density at the electrode/dielectric interface in terms of Fermi level pinning (FLP). We found that the Φeff values agree with the values calculated using the interface gap states model with an extrinsic contribution, assuming that the interface gap state density is proportional to the product of Hf density in the dielectric and Si density in the electrode at the electrode/dielectric interface. On the basis of our results, we discuss the origins of FLP at the electrode/Hf-based dielectric interface.