X-RAY PHOTOELECTRON STUDY OF TIN/SIO2 AND TIN/SI INTERFACES

The TiN/SiO2 interface has been studied using X-ray photoelectron spectroscopy (XPS). The underlying layer of SiO2 was thermally grown on a Si substrate. A thin film of TiN was then deposited on a SiO2/Si substrate by low-pressure chemical vapor deposition using a mixture of TiCl4, NH3 and H-2 gases. In another type of sample, a reactive sputtering (physical vapor deposition (PVD)) technique was employed to deposit the TiN film on the SiO2/Si substrate. In this process a pure Ti target was sputtered in a N-2 and Ar plasma in a d.c. magnetron system. The Ti 2p, N 1s, 0 1s and Si 2p regions were investigated by XPS for chemical reactivity at the TiN/SiO2 interface. In both these samples a shoulder was observed on the high binding energy side of the main N 1s peak at the beginning of the TiN/SiO2 interface. The intensity of this shoulder increases while that of the main N 1s peak bonded to Ti decreases as a function of depth. No spectral changes were observed for films produced by PVD. The presence of this shoulder is attributed to the formation of silicon oxynitride at the interface. Pauling's electronegativity criterion supports this conclusion.