The Study of Ultrathin Tantalum Oxide Films before and after Annealing with X-Ray Photoelectron Spectroscopy

The effects of post-deposition annealing on the microstructure of tantalum oxide ( Ta2O5) deposited on Si are evaluated by means of X-ray photoelectron spectroscopy. With the peak decomposition technique and the angle-resolved X-ray photoelectron spectroscopy (ARXPS) method we found that there is SiO2 layer and Ta suboxide at the interface. By using a simple two-layer model, the thickness of both the Ta2O5 layer and the interfacial SiO2 layer could be evaluated. Investigating Ta2O5 films this way before and after annealing revealed that annealing has the following effects on the interfacial reaction. With post-deposition annealing under O2, Ar, or N2 gas, the Si substrate is oxidized by oxygen from the Ta2O5 layer. The Ta2O5 is partly reduced and N2 gas activates this reaction. The thickness of the interfacial SiO2 layer is reduced by nitridation of the Si substrate.