Suppression of Charges in Al₂O₃ Gate Dielectric and Improvement of MOSFET Performance by Plasma Nitridation

We studied nitrogen incorporation in Al₂O₃ gate dielectrics by nitrogen plasma and examined the dependence of the electrical properties on the nitrogen incorporation. We found that the nitrogen concentration and profile in Al₂O₃ films thinner than 3 nm can be controlled by the substrate temperature and the plasma conditions. The electrical characterization showed that the plasma nitridation suppresses charges in Al₂O₃ films and prevents dopant penetration through the gate dielectric without increasing the leakage current or the interfacial trap density. We also demonstrated the improved performance of a metal-oxide-semiconductor field effect transistor by using a plasma nitrided Al₂O₃ gate dielectric. These results indicate that plasma nitridation is a promising method for improving the electrical properties of Al₂O₃ gate dielectrics.