Paper EM-FrM1
Electrical Properties of High k Dielectrics Improved by Atomic Scale Nitrogen Depth Profile

Friday, October 19, 2007, 8:00 am, Room 612

Nitrogen incorporation produces several benefits in the performance of high k gate oxides. However, since too much nitrogen incorporation at the interface of gate dielectric can result in device degradation, the atomic scale control of nitrogen depth profile is desirable. In this study, we have improved the electrical properties of gate oxides, including dielectric reliability and interface state density, by depth profile control using in situ nitrogen incorporation during plasma enhanced atomic layer deposition (PE-ALD). The PE-ALD HfO₂ films with oxygen plasma and PE-ALD HfO_xN_y films with N/O mixture plasma were prepared at various growth conditions, changing nitrogen profile (bottom, middle and top) and N/O flow ratio (from 0 to 4). The best electrical properties in terms of hysteresis, EOT, and interface state density were obtained when the nitrogen was incorporated in the middle of the thin film with the N/O ratio of 2, which has not been achievable by other nitridation techniques. The EOT and interface state density of middle nitridation sample was reduced to 0.95nm (HfO₂ : 1.10nm) and 0.75x10¹¹cm^-2eV^-1 (HfO₂ : 1.20x10¹¹cm^-2eV^-1). Also, the 50% failure electric field was improved from -10.3 MV/cm to -12.2 MV/cm.