Reduced oxygen precipitation in heavily arsenic-doped Cz-silicon crystals

Oxygen precipitation in heavily arsenic doped Czochralski silicon is investigated for a wide dopant concentration range (from 3 × 1018 cm–3 to 4 × 1019 cm–3) and it is compared with that observed in lightly doped silicon having similar initial oxygen concentration. A lower density of oxide precipitates after an anneal of 4 h at 800 °C followed by 16 h at 1000 °C is measured in the case of arsenic doped samples, in comparison to lightly doped ones, when the dopant concentration exceeds 1.6 × 1019 cm–3. In addition, no radial bands (rings) of precipitation are observed in arsenic-doped samples, contrary to lightly doped samples grown at the same V/G (ratio between pull rate V and axial thermal gradient G). These findings are explained by considering the role played by vacancies in the formation of oxygen precipitates and the impact of the arsenic concentration on the total concentration of point defects in silicon. Data obtained by computer simulation of microdefect formation in silicon are also presented in support of this explanation. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)