Lanthanum implantation for threshold voltage control in metal/high-k devices

In this paper the tuning of the n-metal effective work function by implantation of lanthanum is demonstrated. The effect of implantation and thermal annealing on the device flat-band voltage is presented. It is shown that lanthanum doping of the gate stack produces a negative shift of the flat-band voltage of −0.53 V for a lanthanum does of 5 × 1014 cm−2, after the device undergoes S/D anneal conditions. The results are discussed within the framework of a phenomenological dipole model and compared with other results