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 SiO ₂ 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-Si _3-x N _x ] ₃ N chemical state, N atoms in the (Si-Si _3-x O _x ) ₃ N chemical state of about two monolayers, and the top SiO ₂ 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-Si _3-x N _x ] ₃ N lower layer and the (Si-Si _3-x O _x ) ₃ N upper layer with the concentration of 3.9×10 ¹⁴ and 1.7×10 ¹⁴ cm ^-2 , respectively, based on the N 1s chemical shift of about 0.6eV.