Investigation of the mechanism of Si self-interstitial injection from nitridation of SiO2 films
Abstract
We have performed a set of experiments to determine the cause of Si self-interstitial injection that occurs during nitridation of SiO2 films (oxynitridation). Using oxidation and nitridation reactions we have found that: the lateral decay length of interstitials in an oxidation-enhanced-diffusion (OED) experiment is much longer under a nitrided oxide compared to an un-nitrided oxide; diffusion under a nitrided oxide can be different than diffusion under a pad oxide, even at Ar atmosphere; the amount of enhanced diffusion of P under a nitriding oxide decreases as the area of the oxide exposed to NH3 decreases. SUPREM IV simulations show that a consistent explanation for oxidation and oxynitridation results can be achieved by assuming that during oxynitridation, surface generation and reabsorption fluxes of self-interstitials are both much smaller than similar surface fluxes that occur during oxidation. Further experiments show that Ga diffuses easily through nitrided oxides (as it does through SiO2) whereas CVD and thermally grown Si3N4 act as diffusion barriers.