Effectiveness of aluminum incorporation in nickel silicide and nickel germanide metal gates for work function reduction

Abstract

In this paper, nickel-aluminum (Ni1-xAlx) alloys were employed for Al incorporation in nickel suicide (NiSi) and nickel germanide (NiGe) metal gates [denoted by Ni(Al)Si and Ni(Al)Ge, respectively] to achieve n-channel metal-oxide-semiconductor (NMOS) work function Φm tunability. A higher annealing temperature during gate formation was found to increase Al concentration at the gate/dielectric interface. The presence of low Φm Al at the gate/dielectric interface reduces the NiSi and NiGe Φm by ∼0.2 and ∼0.6eV, respectively. However, the saturation in both Ni(Al)Si and Ni(Al)Ge gate Φm at ∼4.4 eV is due to Fermi-pinning from the formation of interfacial Al2O 3 which prevented a further lowering in Φm to that of pure Al (∼4.1-4.3eV). © 2008 The Japan Society of Applied Physics.