We have incorporated several percent of nitrogen only near the top surfaces of thermally grown oxides by exposure to fluorine gas at room temperature followed by an atomic nitrogen treatment at 550°C. The depth profiles and the bonding of incorporated nitrogen atoms have been studied by angle-resolved x-ray photoelectron spectroscopy.
MOS devices were fabricated using the nitrided oxide with boron doped polycrystalline silicon gate. From the capacitance-voltage measurements we confirmed that the nitrided oxide would prevent the boron penetration in comparison with the conventional oxide films. The proposed technique identifies a unique process for obtaining high quality ultrathin dielectrics.