Backside oxidation/frontside stacking-fault growth experiments were carried out to study the behavior of silicon self-interstitials injected during wet and dry oxidations of the backside of thinned samples. The concentration of self-interstitials at the capped surfaces was monitored by the growth or shrinkage of surface stacking faults. From the analysis of the experimental results, the relative recombination rates of self-interstitials at oxide and nitride boundary layers were obtained, with an oxide layer found to absorb self-interstitials at about three times the rate of a nitride layer. The results also suggest that the surface recombination coefficients are time-dependent rather than constant, as has been previously assumed.