Neutron irradiation defects in Czochralski silicon

Abstract

AbstractIn this paper the influence of neutron irradiated on the defects and oxygen precipitation in Czochralski silicon were investigated. The vacancy‐oxygen complex (VO, A‐center) is one of the main defects formed in neutron‐irradiated Czochralski silicon (CZ‐Si). In this defect, the oxygen atom shares a vacancy, it is bonded to two silicon neighbours. Annealing of the A‐center in varied neutron‐irradiated CZ‐Si consists of two processes. The first is trapping of VO by interstitial oxygen (Oi) in low‐dose neutron‐irradiated CZ‐Si and the second is capturing of the wandering vacancy by VO, etc, in high‐dose neutron‐irradiated CZ‐Si. With the increase of the irradiation dose, the annealing behavior of the A‐center is changed and the formation of the VO2 is depressed. It is found that V2 and V4 abound in high‐dose irradiated CZ‐Si. With the increase of the annealing temperature the monovacancy type defect is annihilated. The results show that the formation of V4 is enhanced when the annealing temperature ran up to 400‐600 °C and with the FTIR absorption peak at the wave number of 829 cm–1 (VO) disappearing, five absorption peaks appear. It can be concluded that these defect‐impurity complexes prolong the lifetime of positrons. It is found that the high‐dose irradiated greatly accelerates the oxygen precipitation which leads to a sharp decrease of the interstitial oxygen with the increase of the annealing time. At room temperature, the 1107 cm–1 infrared absorption band of interstitial oxygen becomes weak and broadens to low energy side. The bulk micro‐defects, including stacking faults, dislocations and dislocation loops, were observed by the optical microscopy. New or large stacking faults grow up when the silicon self‐interstitial atoms are created and aggregate with oxygen precipitation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)