Influence of oxygen and nitrogen on point defect aggregation in silicon single crystals

Oxygen- and nitrogen-doped floating zone (FZ) crystals were investigated with regard to radial oxygen precipitation, D-defect formation and gate oxide integrity (GOI) behavior as a function of the nitrogen content. It is shown that the inactivation of the nitrogen-enhanced D-defect suppression and GOI improvement is not a result of the reduction of the N-pair concentration due to nitrogen-oxygen interaction. Instead, 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 between vacancies and interstitials, which was previously proposed to explain the simultaneous suppression of vacancy- and Si interstitial-type defects 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 radius of oxygen precipitates which accounts for the influence of vacancies and self- interstitials. A qualitative picture of the radial variation of the vacancy and interstitial concentrations is derived assuming that D-defect formation occurs before the onset of oxygen precipitation.