Impact of ambient atmosphere on as-implanted amorphous insulating layers

Low energy ion implantation into SiO2 causes a damaged near surface layer. The high number of broken bonds due to displaced Si and O atoms forms in the glassy network pathes, which are open for diffusion and in which moisture from the ambient can be absorbed. Therefore chemical reactions of the implanted impurities with hydrogen and oxygen must be expected during subsequent annealing. Water absorption in heavy ion-damaged SiO2 layers has been studied by hydrogen depth profiling using the Nuclear Reaction Analysis (NRA). SiO2 was implanted with ions of different mass (Si, Ge, Sn) and doses in the range 1013...1016 cm-2. H depth profiles were measured after storage under clean room conditions and after additional wet cleaning, as well as after annealing. At the surface and in the region of the implanted profile, the H concentration reaches 5-10 at% after storage and increases during wet chemical cleaning up to 12 at% for implantation doses >1x1014 cm-2.