Substituted aluminum metal gate on high-k dielectric for low work-function and Fermi-level pinning free

Substituted aluminum (SA) metal gate on high-K gate dielectric is successfully demonstrated. Full substitution of polysilicon with Al is achieved in Ti/Al/polysilicon/HfAlON gate structure by a low temperature annealing at 450/spl deg/C. The SA gate on HfAlON dielectric shows a very low work function of 4.25 eV, which is well suitable for bulk nMOSFETs. The SA process is fully free from Fermi level pinning problem. In addition, the SA process also shows improved uniformity in leakage current distribution compared to fully silicided (FUSI) metal gate.