Achieving Conduction Band-Edge Effective Work Functions by $\hbox{La}_{2}\hbox{O}_{3}$ Capping of Hafnium Silicates

Conduction band-edge effective work functions (phi m,eff ) are demonstrated with TaC x and TiN by means of La 2 O 3 capping of HfSiO x in a gate-first process flow with CMOS-compatible thermal budget. With TaC x , a 10- Aring-thick La 2 O 3 cap results in a phi m,eff of 3.9 eV with a low equivalent oxide thickness (EOT) increase (1-2 Aring) and unaffected electron mobility. With TiN, non-nitrided La 2 O 3 capping results in a smaller phi m,eff reduction at a larger EOT increase, while with post-cap nitridation, the TiN phi m,eff is lower at a smaller EOT increase. Results show that the choice of metal and nitridation conditions have significant effects on La 2 O 3 capped stacks