Physical and electrical properties of lanthanide-incorporated tantalum nitride for n -channel metal-oxide-semiconductor field-effect transistors

Abstract

Lanthanide-incorporated tantalum nitride (TaN) is studied as a potential metal gate candidate for n -channel metal-oxide-semiconductor field-effect transistors (n -MOSFETs). Lanthanides such as terbium (Tb), erbium (Er), and ytterbium (Yb) are introduced into TaN to form Ta1-x Tbx Ny, Ta1-x Erx Ny, and Ta1-x Ybx Ny metal gates, respectively, on Si O2 dielectric. The resistivity, crystallinity, film composition, and work function of Ta1-x Tbx Ny, Ta1-x Erx Ny, and Ta1-x Ybx Ny films were investigated at different post-metal-anneal temperatures and for different lanthanide concentrations. It was found that the work function of lanthanide-incorporated TaN can be effectively tuned by increasing the concentration of lanthanide. Work functions of about 4.2-4.3 eV can be achieved even after a 1000 °C rapid thermal anneal, making lanthanide-incorporated TaN a promising metal gate candidate for n -MOSFETs. The enhanced nitrogen concentration and the possible presence of lanthanide-N or Ta-N-lanthanide compounds in lanthanide-incorporated TaN film could be responsible for its chemical-thermal stability on Si O2. © 2005 American Institute of Physics.