Interfacial chemistry and structures of ultrathin Si oxynitride films

Ultrathin SiON films with different nitrogen profiles grown by the plasma-enhanced CVD method and the rapid thermal nitridation (RTN) of SiO2 with an NO gas have been analyzed by high-resolution angle-resolved photoelectron spectroscopy using bright synchrotron radiation to investigate interfacial chemistry and in-depth distribution of nitrogen atoms based on the second nearest neighbor effect of N 1s chemical shift. It is found that the CVD-deposited SiON film has a three-layer structure consisting of homogeneously-distributed N atoms in the [Si-Si3−xNx]3N chemical state, N atoms in the (SiSi3−xOx)3N chemical state of about two monolayers, and the top SiO2 layer. In contrast, N atoms in the NO-RTN SiON film exist at the SiON/Si interface as a double layer consisting of the [Si-Si3−xNx]3N lower layer and the (SiSi3−xOx)3N upper layer with the concentration of 3.9×1014 and 1.7×1014 cm−2, respectively, based on the N 1s chemical shift of about 0.6 eV.