Effective work function changes in TiN/HfO2 annealed at low temperatures in different ambient environments were correlated with the atomic concentration of oxygen in the TiN near the metal/dielectric interface. The effective work function increases of 550meV were achieved with anneals that incorporate oxygen throughout the TiN with [O] = 2.8 x 1021/cm3 near the TiN/HfO2 interface. However, further increasing the oxygen concentration via more aggressive anneals resulted in a relative decrease of the effective work function and increase in electrical thickness. First-principles calculations indicated the exchange of O and N atoms near the TiN/HfO2 interface cause the formation of dipoles that increased the effective work function.

Interfacial Oxygen and Nitrogen Induced Dipole Formation and Vacancy Passivation for Increased Effective Work Functions in TiN/HfO2 Gate Stacks. C.L.Hinkle, R.V.Galatage, R.A.Chapman, E.M.Vogel, H.N.Alshareef, C.Freeman, E.Wimmer, H.Niimi, A.Li-Fatou, J.B.Shaw, J.J.Chambers: Applied Physics Letters, 2010, 96[10], 103502