Annealing Kinetics of the Interstitial Carbon–Dioxygen Complex in Silicon

Abstract

The interstitial carbon-interstitial dioxygen complex (C i O 2i ) has a deep state close to the mid bandgap of Si and can be an efficient recombination center. In this work, the annealing kinetics of C i O 2i in p-type, boron doped, Czochralski grown (Cz) silicon are studied. Two sets of samples are irradiated at room temperature (RT) with 1.8 MeV protons to doses of 1 Â 10 13 cm À2 (set A) and 5 Â 10 13 cm À2 (set B). After irradiation, the samples of both sets are pre-annealed at 400 C for 30 h in order to anneal out the well-known interstitial carbon-interstitial oxygen (C i O i ) complex and to form the C i O 2i complex. The annealing of C i O i and formation of C i O 2i is monitored by deep level transient spectroscopy (DLTS) via observation of the corresponding electronic levels at 0.36 eV and 0.39 eV above the valence band edge (E V ), respectively. The samples are then subjected to isothermal annealing treatments in the temperature range 450-550 C. The annealing of C i O 2i follows a first order kinetics, exhibiting an activation energy of 2.55 eV, and a pre-exponential factor in the range (2-30) Â 10 12 s À1 . The kinetics and the deduced parameters suggest that C i O 2i anneals out by dissociation rather than diffusion mechanism.

The Interstitial Carbon–Dioxygen Center in Irradiated Silicon

“…These conclusions are in agreement with previous PL and DLTS measurements referring to the investigation of the C i O 2i defect [18,19]. It was suggested that the annealing of the C i O i occurs via dissociation into C i and O i , where a percentage of the released C i atoms are trapped by oxygen dimers to form the C i O 2i [17,18].…”

“…This might result in more stable defects, which may need a higher temperature to anneal out. Additionally, the detected signal in our IR studies could refer to different states of the same defect reported in previous photoluminescence (PL) and DLTS measurements [17][18][19]. Further clarification of this issue requires future work.…”

“…Regarding the differences in the formation temperature of the C i O 2i defect between our electron irradiated samples and proton irradiated samples [17][18][19], the following should be noted: Proton irradiation generates higher order of damage than electron irradiation. This might result in more stable defects, which may need a higher temperature to anneal out.…”

“…An important point: In our studies of electron irradiated silicon, the 1020 cm −1 band is formed around 300 • C upon the decay of the 862 cm −1 band of the C i O i pair. However, in proton-irradiated thermally treated Si, the formation of the C i O 2i occurs at temperatures above 400 • C according to the reaction C i +O 2i → C i O 2i [17][18][19]. The suggested mechanism in the latter reports involves the dissociation of the C i O i and the capture of the liberated carbon interstitials by oxygen dimers.…”

“…Early photoluminescence (PL) studies reported thermal treatments at 350-450 • C, have correlated the decay of the C-line (789.5 meV) of the C i O i defect with the growth of the P-line (767 meV) attributed to the C i O 2i defect [1,16]. Recent deep level transient spectroscopy (DLTS) studies have monitored the decay of the C i O i pair and the formation of the C i O 2i structure via the observation of the corresponding electronic levels at E V + 0.36 eV and E V + 0.39 eV [17] . These conclusions are in agreement with previous PL and DLTS measurements referring to the investigation of the C i O 2i defect [18,19].…”