Energy spectroscopy studies of radiation-induced damaged surfaces and interfaces in SiO2/Si by light charged particles

In this paper, the three different experimental techniques of AES (Auger electron spectroscopy), ARXPS (angle-resolved X-ray photoelectron spectroscopy) and DLTS (deep level transient spectroscopy) with C-V measurements have been applied to study damaged surfaces and interfaces of SiO2-Si in MOS. The defects, appearing at the surface of the dielectric layer and the interface between SiO2 and Si, induced by energetic electron and/or hydrogen ion (H+) beams, were independently investigated using ARXPS and AES combined with DLTS, respectively. The more intermediate oxidation states, such as Si1+, Si2+ and Si3+, corresponding to Si2O, SiO and Si2O3 clusters formed at the surface and the transition regions, were obtained for the irradiated sample. The changes of the intensity, full width at half maximum (fwhm) and binding energy of each ARXPS spectrum with take-off angle showed that silicon-rich clusters or chains, and about 4.8A of an amorphous silicon, actually existed in the outermost surface as a result of preferential sputtering of oxygen by electron ionization and displacement by H+. The Si2p core-level spectra were analyzed in terms of five chemically shifted components corresponding to the basic Si binding units Si-On with n=0, 1,..., 4. The concentration of these bonding units as a function of effective depth of emission was essentially in agreement with the random-bonding model. But some separation into a silicon-rich phase was also evident at intermediate stoichiometries and stacks. In addition, more dangling bonds of Si were present overall in the oxide layer, which acted with an amphoteric character and caused the defect states to lie in the lower half of the bandgap. (orig.)