Properties of Anodically Oxidized Silicon Films Implanted with High Doses of CO⁺ Ions

Properties of anodically oxidized layers of silicon implanted with CO ⁺ ions with energy of 90 keV depending on the ion dose from 2.5× 10¹⁵ to 3× 10¹⁶ cm ⁻² have been studied. After ion implantation, the samples were annealed at a temperature of 700 ∘ C for 1 h in the N ₂ vapor atmosphere. The oxidized layers were analyzed using spectral ellipsometry, atomic force microscopy, and infrared spectroscopy. The refractive index of the oxidized layers exceeded that of thermally grown SiO ₂ and decreased from 1.58 to 1.52 with increasing CO ⁺ ion dose from 2.5× 10¹⁵ to 1× 10¹⁶ cm ⁻² . As the CO ⁺ dose increased, an increase in the infrared absorption at CO ₂ molecules was observed in the anodic oxide films. The dose dependence of the refractive index of anodically oxidized layers is discussed from the viewpoint of formation of microvoids in silicon oxide during evaporation of CO ₂ molecules.