Profiling nitrogen in ultrathin silicon oxynitrides with angle-resolved x-ray photoelectron spectroscopy

Angle-resolved x-ray photoelectron spectroscopy (AR-XPS) is utilized in this work to accurately and nondestructively determine the nitrogen concentration and profile in ultrathin SiO_xN_y films. With furnace growth at 800-850 °C using nitric oxide (NO) and oxygen, 10¹³-10¹⁵ cm^-2 of nitrogen is incorporated in the ultrathin (≤4 nm) oxide films. Additional nitrogen can be incorporated by low energy ion (¹⁵N₂) implantation. The nitrogen profile and nitrogen chemical bonding states are analyzed as a function of the depth to understand the distribution of nitrogen incorporation during the SiO_xN_y, thermal growth process. AR-XPS is shown to yield accurate nitrogen profiles that agree well with both medium energy ion scattering and secondary ion mass spectrometry analysis. Preferential nitrogen accumulation near the SiO_xN_y/Si interface is observed with a NO annealing, and nitrogen is shown to bond to both silicon and oxygen in multiple distinct chemical states, whose thermal stability bears implications on the reliability of nitrogen containing SiO₂.