Intrinsic correlation between mobility reduction and Vt shift due to interface dipole modulation in HfSiON/SiO2 stack by La or Al addition

Intrinsic correlation between mobility reduction by remote Coulomb scattering (RCS) and threshold voltage shift (DeltaV_t), both of which are induced by interface dipole modulation at high-k/SiO₂ interface, is investigated. Three types of dipole modulation are examined; Al addition, La addition, and changing quality of interfacial SiO₂ layer. Extrinsic scattering components due to increases of interface state and surface roughness are extracted and separated. It is found that RCS due to interface dipole modulation by Al addition increases with increasing DeltaV_t, while that by La addition is constant, independent of DeltaV_t. Inevitability of additional scattering for DeltaV_t is discussed based on two different models for dipole formation mechanisms.