Helium ion-induced stoichiometry modification in hydrogenated silicon oxide films

The stoichiometry of amorphous hydrogenated silicon oxide films, grown in a dual-plasma system, has been investigated using elastic recoil detection (ERD), Rutherford backscattering, and infrared transmission. During ERD measurement of H profiles, using a He-4(2+) beam of 3.0 MeV, ion-induced depletion of hydrogen atoms was observed, homogeneous over the 1 mu m film thickness. Si-rich films (with H essentially bonded as Si-H) and nearly stoichiometric films (with H only bonded in Si-OH configurations) have been compared. The depletion is more pronounced in nearly stoichiometric oxides, whereas the apparent cross sections (approximate to 1-2 nm(2)) are similar for both types of films. These observations are discussed in terms of an electron excitation process, with a subsequent chemical reconstruction via electron-hole recombination. (C) 1996 American Institute of Physics.