Control of nitrogen depth profile near silicon oxynitride/Si(100) interface formed by radical nitridation

Depth profiles of composition and chemical structures in radical nitrided silicon oxynitride films formed with Ar/N2, Xe/N2, or Ar/NH3 plasma excited by microwave have been investigated by X-ray photoelectron spectroscopy combined with step etching in HF solution. The relationship between the intensities of emission from N2+ radical in these plasmas and the concentration of nitrogen atoms forming Si3≡N configuration near the silicon oxynitride film/Si substrate interface nitrided using these plasmas was studied. The emission intensities from N2+ radical generated in Xe/N2 or Ar/NH3 plasma are a quarter or one-sixth of that from N2+ radical generated in Ar/N2 plasma respectively. However, the emission from NH radical is also detected in Ar/NH3 plasma. Although the nitrogen concentration of Xe/N2 plasma is smaller than that of Ar/N2 plasma at the film/substrate interface, that of Ar/NH3 plasma is larger than that of Ar/N2 plasma at the interface. It is important for the reduction of the nitrogen concentration near the film/substrate interface to use Xe/N2 plasma in which both of the generation efficiencies of N2+ and NH radicals are low.