Interface structure of ultrathin oxide prepared by N/sub 2/O oxidation

With X-ray photoelectron spectroscopy (XPS) measurements, we found in the N/sub 2/O-grown oxide that the nitrogen incorporation should involve the NO or N reaction with the Si-Si bond and P/sub b/ centers at the interface. Consequently, nitrogen content is very low and accumulated mainly at the interface. In addition, we found that the nitrogen atoms at the interface exist in the form of Si-N bonding and the interface oxynitride layer is a mixture of SiO/sub 2/ and Si/sub 3/N/sub 4/ clusters. This structure will result in several undesirable effects. It will give rise to the permittivity and bandgap fluctuations at the interface and hence induced gigantic surface potential fluctuation and mobility degradation in the channel of MOS devices. This bonding structure also explains the interface trap generation during the electrical stressing. The sources of trap generation are attributed to the Si-Si bonds, P/sub b/ centers, and nitride-related defects due to the over-constrained silicon atoms in the Si/sub 3/N/sub 4/ clusters at the interface.