A significant increase of HF etching rate and mean surface roughness (monitored by atomic force microscopy) was observed after P ion implantation on thin thermal SiO2 films (15nm). The dependence upon the ion fluence (ranging from 3 x 1012 to 5 x 1013/cm2) and energy (ranging from 270 to 500keV) was analyzed, together with the recovery effect of post-implantation annealing in N2 atmosphere. Moreover, the impact of P implants on oxides grown by different sequences, considering post-oxidation annealing in N2O or N2 atmospheres, was also studied. The effect of ion irradiation was investigated by thermally stimulated luminescence above room temperature in order to obtain information on point defects present in the layers. The results showed that post-oxidation annealing treatments in N2 atmosphere carried out not only after, but also before ion implantation, were particularly useful in lowering the concentration of thermally stimulated luminescence active defects. This could be attributed to the role played by N2 annealing in favoring a structural rearrangement of the SiO2 layers.

Phosphorous Implantation in Silicon through Thin SiO2 Layers - Oxide Damage and Post-Oxidation Thermal Treatments. A.Vedda, M.Martini, G.Spinolo, B.Crivelli, F.Cazzaniga, G.Ghidini, M.E.Vitali: Journal of Applied Physics, 2001, 90[10], 5013-7