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

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 Ta 1 − x Tb x N y , Ta 1 − x Er x N y , and Ta 1 − x Yb x N y metal gates, respectively, on Si O 2 dielectric. The resistivity, crystallinity, film composition, and work function of Ta 1 − x Tb x N y , Ta 1 − x Er x N y , and Ta 1 − x Yb x N y 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 O 2 .