Incorporation of nitrogen in thin tantalum films using plasma immersion ion implantation

The incorporation of nitrogen into thin (10 nm) Ta layers using plasma immersion ion implantation (PIII) has been studied. PIII was carried out using a low-pressure (0.3 Pa) plasma and ion energies between 6 and 25 keV. The depth distributions of nitrogen were measured by Auger electron spectroscopy (AES) and compared with those obtained by numerical simulations (Profile Code). The experimental profiles do not show a maximum at the projected range of the implanted ions, but a high nitrogen concentration at the surface decreasing with depth. The influence of implantation parameters such as high-voltage pulse rise and fall times, voltage amplitude, and plasma pulsing on the shape of the nitrogen profile is investigated and discussed. Especially reduced fall time of the high-voltage pulse reduces the implantation with energies below the nominal value and therefore the high nitrogen concentration near the surface significantly.