Material and electrical characterization of carbon-doped Ta2O5 films for embedded dynamic random access memory applications

This work is a systematic study of carbon incorporation in Ta2O5 and its effect on the material and electrical properties of Ta2O5, a promising replacement for silicon oxide in embedded dynamic random access memory applications. Using pulsed-dc reactive and rf-magnetron sputtering of Ta2O5 performed in an argon/oxygen/carbon-dioxide plasma, we have methodically doped the Ta2O5 films with carbon. In thick (70 nm) Ta2O5 films, an optimal amount (0.8–1.4 at. %) of carbon doping reduced the leakage current to 10−8 A/cm2 at +3 MV/cm, a four orders of magnitude reduction compared to a leakage current of 10−4 A/cm2 in an undoped Ta2O5 film grown in similar conditions without CO2 in the plasma. This finding suggests that carbon doping can further improve the dielectric leakage property at an optimal concentration. X-ray Photoemission Spectroscopy analysis showed the presence of carbonate (carbon bonded to three oxygen) in these electrically improved carbon-doped films. Analysis by high-resolution transmission ele...