INFLUENCE OF OXYGEN AND NITROGEN ON POINT-DEFECT AGGREGATION IN SILICON SINGLE-CRYSTALS

Oxygen- and nitrogen-doped floating zone (FZ) crystals were investigat ed with regard to radial oxygen precipitation, D-defect formation and gate oxide integrity (GOI) behavior as a function of the nitrogen cont ent. It is shown that the inactivation of the I nitrogen-enhanced D-de fect suppression and GOI improvement is not a result of the reduction of the N-pair concentration due to nitrogen-oxygen interaction. Instea d, it is suggested that the diffusivity of vacancies, Si interstitials and nitrogen is reduced due to interaction with oxygen. This leads to a considerable decrease in the nitrogen- enhanced recombination betwe en vacancies and interstitials, which was previously proposed to expla in the simultaneous suppression of vacancy- and Si interstitial-type d efects by nitrogen doping. The radial oxygen precipitation behavior is explained by applying the formula of Vanhellemont and Claeys (J. Appl . Phys., 62 (9) (1987) 3960; 71 (2) (1992) 1073) for the critical radi us of oxygen precipitates which accounts for the influence of vacancie s and self-interstitials. A qualitative picture of the radial variatio n of the vacancy and interstitial concentrations is derived assuming t hat D-defect formation occurs before the onset of oxygen precipitation .