Improved surface nitridation of SiO2 thin films in low ammonia pressures

Surface nitridation of thin SiO2 films (130 Å) has been achieved in low ammonia pressures (P≤10−1 mbar) by thermal activation (900 °C≤T≤1050 °C) or by electron-beam-enhanced reaction at room temperature. In the first case, the nitridation rate increases with P, T, and time t; in the latter, it depends on P, t, electron energy and flux, and reaches a maximum within the energy range (1–∼1.7 keV). Electrical characterization of metal-insulator-semiconductor structures shows that the SiO2/Si interfacial quality is not damaged as long as interfacial nitrogen concentration remains negligible. However, bulk and/or interfacial fixed positive charges are detected in the SiO2 films nitrided at room temperature.