Formation of Mo gate electrode with adjustable work function on thin Ta2O5 high-k dielectric films

Formation of Mo gate electrode with adjustable work function on thin Ta2O5 high-k dielectric films at low-temperature processing of 600 °C has been studied by using nitrogen implantation into the Mo gate electrode. For the sample without nitrogen implantation, a work function of about 4.85 V can be achieved for p-FET. By employing the nitrogen implantation into the Mo gate electrode, a work function of about 4.45 V can be achieved for n-FET. Though larger nitrogen implantation energy can lead to even lower work function as 4.25 V, much larger capacitor leakage is caused and capacitance value is considerably degraded, attributable to the penetration of nitrogen into Ta2O5 dielectrics. As a result, proper nitrogen implantation energy should be employed to make trade-off of capacitance value, capacitor leakage, and work function, for high-performance nanometer CMOS IC technology.