XPS INVESTIGATION ON THE GROWTH-MODEL OF A-SINX AND SILICON AND NITROGEN CHEMICAL BONDINGS

Amorphous silicon nitride a-SiNx (0 < x < 1.7) thin films, prepared by Dual Ion Beam Sputtering (DIBS) technique, were investigated by means of high energy resolution X-ray Photoelectron Spectroscopy (XPS) using a monochromatize radiation. The variation of the position, width and lineshape of the Si2p and Nls photoemission peaks, as well as the X-ray-induced Auger Electron Spectra (XAES) of N(KVV), Si(LVV), and Si (KL2,3L2,3), as function of the alloy composition, were explained for silicon in terms of a superposition of five chemically-shifted unresolved components corresponding to the five tetrahedral silicon bonding configurations Si-Si4 - n(N)n (n - 0.1 ...4) and for nitrogen a single bonding configuration with three silicon surrounding atoms. By a curve fitting process, we obtained the Si-Si4-n(N)n distribution as a function of atomic composition and compared it with the predictions of the most used growth models: the Random Bonding Model (RBM) and the Stoichiometric Statistical Model (SSM). These two models were not in good agreement with the experimental data thus, another model was proposed based on the invariant coordination of nitrogen to three silico neighbours, and including a nucleation of possible stoichiometric clusters in the a-SiNx film structure. Moreover, methodological aspects, such as artifacts induced by ion sputtering, which was used to clean the smaple surface before XPS measurements, were taken into account.