Understanding of CO2 interaction with thermally grown SiO2 on Si using IBA depth profiling techniques

Interactions between CO2 and SiO2 films thermally grown on Si have been studied using 18O and 13C as isotopic tracers associated with ion beam analysis (IBA) depth profiling techniques. From secondary ion mass spectrometry (SIMS) measurements no carbon from CO2 is detected in the silica while it is found in Si. These results suggest that CO2 diffuses through the silica. Exchanges of oxygen between CO2 and silica can be observed from 18O to 16O SIMS signals variation. The oxygen concentration depth profiles were determined quantitatively using the narrow resonance near 151 keV in the 18O(p,α)15N nuclear reaction (Narrow Resonance Profiling, NRP). We demonstrate that two distinct oxygen exchanges processes co-exist and we determine the diffusion coefficient of the CO2 molecule in the silica at 1100 °C.