N-type VT tuning by Te ion implantation in moly-based metal gates with high-k dielectric for fully depleted devices

In the framework of fully depleted devices, we report up to 150 mV V_T tuning towards the Si conduction band by implantation of Te into molybdenum capped with TiN, the dielectric being HfO₂. Moderate post implant anneal seems to have no effect on the V_T shift while high temperature anneal is needed to shift the EWF significantly. The temperature applied to the devices during the entire process is therefore crucial for driving the implanted species towards the Mo/high-k interface, where they can modify the interface dipole and hence modify the effective workfunction. Hence, high temperature standard pike anneal is a very interesting option. The effective workfunction shifts linearly with the dose. Moreover, the higher the implant energy, the larger the effect of the dose on the effective workfunction. Up to 10 keV, the device integrity is preserved after ion implantation. At higher energies, implanted ions penetrate into the high-k, which leads to D_it and subthreshold slope degradation. However, there is no evidence of counterdoping in this later case and gate leakage is hardly increased.