Ion-activated interface adsorption of oxygen during silver deposition on silicon

Abstract

Abstract The process of ion-activated oxygen adsorption on silicon has been investigated using an experimental concept with simultaneous deposition of silver films. Auger electron spectroscopy in combination with sputter depth profiling is subsequently performed to determine the amount of oxygen adsorbed at the AgSi interface. Noble gas ions ( 4 He + , 20 Ne + and 40 Ar + )with energies between 50 and 175 keV were used, and it was found that for substrate temperatures of 300–700 K the oxygen adsorption depends strongly on ion mass, ion energy and ion flux density. For flux densities of 5 × 10 11 cm −2 s −1 or less, adsorption dominates and, in particular, for light-ion bombardment the majority of adsorbed oxygen atoms form chemical bonds with the silicon surface atoms (SiO). However, for heavy ions, physical sputtering starts to compete and limits the effective rate of adsorption. At sufficiently high ion fluxes the adsorption starts to decrease, and for all ions and energies used in this work it is found that, if the electronic energy deposition density exceeds a critical value of about 1.2 × 10 21 eV cm −2 s −1 , dissociation of the SiO bonds prevails with a corresponding loss in the adsorbed oxygen quantity.