Oxygen precipitation and defects in heavily doped Czochralski silicon

Abstract

The oxygen precipitation and defect formations in Czochralski silicon doped with boron, carbon, and tin were studied after a two-step isochronal anneal in the temperature range between 400 and 900 °C. In silicon lightly doped with boron, a characteristic of isochronal transformation of the bulk defects exhibits two distinctive peaks of maximum defect density at around 550 and 725 °C, respectively. Doping with carbon or boron having a tetrahedral covalent radius smaller than silicon reduces the peak height at 550 °C and simultaneously creates a third characteristic peak at around 850 °C. Based upon the experimental results, the pairing reaction between impurities and point defects, and the relative concentrations between charge defects, it is concluded that oxygen precipitation and defects in silicon heavily doped with boron and carbon-doped silicon are similar. In the case of doping with large impurities such as tin, an enhanced oxygen precipitation was observed. An enhanced oxygen precipitation in tin-doped silicon is hypothesized to be due to a formation of tin-vacancy pairs which act either as the centers of localized lattice relaxation or the nucleaton sites for the precipitate nuclei.