The Effect of Thermal Treatments on the Annealing Behaviour of Oxygen-Vacancy Complexes in Irradiated Carbon-Doped Silicon

Abstract

Cz-grown, carbon-doped silicon samples were irradiated by fast neutrons. We investigated the annealing behaviour of oxygen-related defects, by infrared spectroscopy. We studied the reaction channels leading to the formation of various VmOn defects and in particular the VOn defects formed by the accumulation of oxygen atoms and vacancies in the initially produced by the irradiation VO defects, as the annealing temperature ramps upwards. We mainly focused on bands appearing in the spectra above 450 oC. A band at 1005 cm-1 is found to be the convolution of two bands at 1004 and 1009 cm-1. The latter band has the same thermal stability with the 983 cm-1 of the VO4 defect and therefore is also attributed to this defect. The former band has the same thermal stability with three other bands at 965, 1034 and 1048 cm-1. These four bands may be attributed to VOn (n=5,6) defects, although other VmOn complexes are also potential candidates. Furthermore, we found that pre-treatments of the samples at 1000 oC, with or without the application of high hydrostatic pressure lead to an increase in the concentration of the VO2, VO3 and generally VOn defects in comparison with that of the untreated samples.

IR studies of the impact of Ge doping on the successive conversion of VOn defects in Czochralski-Si containing carbon

“…1 together with another four bands at 1037, 1051, 967, and 1005 cm −1 . We notice that the latter four bands have also been detected in neutron irradiated silicon 22 and in a first assessment were generally correlated with V m O n defects. We shall deal first with these bands in an attempt to make a more definitive assignment of the particular structures that give rise to them.…”

“…Importantly, the two bands emerge in the spectra in the temperature range where VO 3 decays out and subsequently their intensity is enhanced when VO 4 decays out. Thus, one could suggest 21,22 the following possible formation reactions for VO 5 defect: ͑VO 3 +O i → VO 4 then VO 4 +O i → VO 5 ͒ or directly VO 4 +O i → VO 5 . It is worth noting that these bands have also been reported previously in room-temperature measurements of electron irradiated Si.…”

“…Also VO 3 and VO 4 defects attract the interest of researchers because they appear in the spectra in the temperature range of 450-600°C which is a usual range of thermal treatments for material processing. Additionally, there are also reports both theoretical and experimental about the VO n ͑n Ͼ 4͒ defects and LVMs bands were generally attributed [18][19][20][21][22] to VO 5 / VO 6 structures, although any definite assignments are still lacking for each one of the VO 5 and VO 6 defects.…”

Radiation effects on the behavior of carbon and oxygen impurities and the role of Ge in Czochralski grown Si upon annealing

“…Actually, such complexes V m O n exist in neutron-irradiated materials in appreciable concentrations. 16 Finally, in the temperature range of about 700°C both vacancy-and interstitialtype large complexes coexist in neutron-irradiated Cz-Si. However, such interstitial-type complexes are believed to be more stable 30 because of their shorter distorted bonds, in contrast to multivacancy complexes.…”

“…[11][12][13][14][15] With increasing temperature of annealing, VO centers are transformed into large V m O n clusters seen in IR spectra up to 750°C. 16 Concurrently, small interstitial clusters are also growing to extended interstitial-type defects, e.g., rodlike defects stable in the same temperature range. 3,17,18 Intrinsic point defects play an important role in growth and evolution of oxygen precipitates.…”