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.