This paper investigates the infrared absorption spectra of oxygen-related complexes in silicon crystals irradiated with electron(1.5MeV) at 360 K.Two groups of samples with low [Oi]=6.9×1017cm 3 and high [Oi]=1.06×1018cm3 were used.We found that the concentration of the VO pairs have different behaviour to the annealing temperature in different concentration of oxygen specimen,it is hardly changed in the higher concentration of oxygen specimen.It was also found that the concentration of VO 2 in lower concentration of oxygen specimen gets to maximum at 450 ℃ and then dissapears at500 ℃,accompanied with the appearing of VO 3.For both kinds of specimens,the concentration of VO 3 reachs to maximum at 550 ℃ and does not disappear completely at 600 ℃.
The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon(CZ-Si) are investigated systemically by using Fourier transform infrared(FTIR) spectrometer and positron annihilation technique(PAT).Through isochronal annealing,it is found that the trend of variation in interstitial oxygen concentration([Oi]) in fast neutrons irradiated CZ-Si fluctuates largely with temperature increasing,especially between 500 and 700 C.After the CZ-Si is annealed at 600 C,the V4 appearing as three-dimensional vacancy clusters causes the formation of the molecule-like oxygen clusters,and more importantly these dimers with small binding energies(0.1-1.0eV) can diffuse into the Si lattices more easily than single oxygen atoms,thereby leading to the strong oxygen agglomerations.When the CZ-Si is annealed at temperature increasing up to 700 C,three-dimensional vacancy clusters disappear and the oxygen agglomerations decompose into single oxygen atoms(O) at interstitial sites.Results from FTIR spectrometer and PAT provide an insight into the nature of the [Oi] at temperatures between 500 and 700 C.It turns out that the large fluctuation of [Oi] after short-time annealing from 500 to 700 C results from the transformation of fast neutron irradiation defects.
A rapid thermal process (RTP) was first introduced into the intrinsic gettering (IG) processes of fast neutron irradiated Czochralski (CZ) silicon. The effect of RTP conditions on bulk microdefects (BMDs) and denuded zone (DZ) was investigated. Fourier transform infrared absorption spectrometer (FTIR) was used to measure the concentration of interstitial oxygen ([Oi]). Bulk microdefects were observed by optical microscope. The results show that, according to the variation of [Oi], it is found that RTP doesn’t change the processes of oxygen precipitation in fast neutron irradiated Czochralski silicon. Perfect denuded zone, dense oxygen precipitates and defects form in the bulk of irradiated samples. With increasing temperature of RTP, the width of denuded zone decreases. Increasing RTP cooling rate, the density of Bulk microdefects increases. DZ forms in the sample that annealed in nitrogen atmosphere.
The difference of annealing behaviors of vacancy-oxygen complex (VO) in varied dose neutron irradiated Czochralski silicon: (S1 5×1017 n/cm3 and S2 1.07×1019 n/cm3) were studied. The results show that the VO is one of the main defects formed in neutron irradiated Czochralski silicon (CZ-Si). In this defect, oxygen atom shares a vacancy, it is bonded to two silicon neighbors. Annealed at 200 ℃, divacancies are trapped by interstitial oxygen(Oi) to form V2O (840 cm-1). With the decrease of the 829 cm-1 (VO) three infrared absorption bands at 825 cm-1 (V2O2), 834 cm-1 (V2O3) and 840 cm-1 (V2O) will rise after annealed at temperature range of 200-500 ℃. After annealed at 450-500 ℃ the main absorption bands in S1 sample are 834 cm-1, 825 cm-1 and 889 cm-1 (VO2), in S2 is 825 cm-1. Annealing of A-center in varied neutron irradiated CZ-Si is suggested to consist of two processes. The first is due to trapping of VO by Oi in low dose neutron irradiated CZ-Si (S1) and the second is due to capture the wandering vacancy by VO, etc, in high dose neutron irradiated CZ-Si (S2), the VO2 plays an important role in the annealing of A-center. With the increase of the irradiation dose, the annealing behavior of A-center is changed.
