(Invited) Band-Edge Effective Work Functions by Controlling HfO₂/TiN Interfacial Composition for Gate-Last CMOS

Abstract

Effective work function (EWF) changes of TiN/HfO 2 annealed at low temperatures in different ambient environments are correlated to the atomic concentration of oxygen, nitrogen, and aluminum at the metal/dielectric interface. Low EWFs (4.0 eV) are obtained by allowing aluminum to migrate to the TiN/HfO 2 interface during a forming gas anneal. High EWFs (5.1 eV) are achieved with anneals that incorporate oxygen throughout the TiN with [O] = 2.8x10 21 cm -3 near the TiN/HfO 2 interface. First-principles calculations indicate the exchange of O and N atoms near the TiN/HfO 2 interface cause the formation of dipoles that increase the EWF.