The Formation Of Metastable Defects And Interact With Oxygen In CZ Silicon

In Czochralski silicon crystals (CZSi) through fast neutron irradiation, formation and conversion of defects were investigated using Fourier transform infrared spectroscopy (FTIR), Positron annihilation technology (PAT) and Scanning electron microscope(SEM).The results showed that fast neutron irradiation induced large quantity of metastable defects which can be the capture centers of positron, positron annihilation average lifetime of samples increased with increasing of irradiation dosage. Positron annihilation average lifetime of irradiation samples through dosage up to 1 × 1018 n.cm-2 tended to constant. Moreover, concentrations of interstitial oxygen in samples changed after fast neutron irradiation. The interstitial oxygen concentration of the samples decreased with increasing of irradiation dosage. This result can be explained in terms of higher generation rates of (V-O) complex.A new vibrational infrared absorption band at about 485cm-1 appeared commonly in spectra of Czochralski-grown and Float-zone-grown silicon irradiated with fast neutron. The new vibrational infrared absorption band was assigned to local vibrational modes related to the complicated complex of irradiation defects that did not contain oxygen atoms. The new vibrational infrared absorption band at about 485cm-1 was annealed at about 400 ℃. It was difficult to annealing V-O complex in fast neutron irradiated Si under 600 ℃ for 1h. After annealing at 600 ℃, because of formation of multi-vacancy-type defects that have long positron lifetime , positron annihilation average lifetime increased. When the average positron lifetime increased to maximum value(360ps), the interstitial oxygen concentration decreased to minimum value(4×1017atoms/cm3). This result suggested that oxygen was involved in the formation of multi-vacancy-type defects.Interact of fast-neutron irradiation defects and oxygen impurity in CZ-Silicon was investigated in this paper. The result suggested that oxygen precipitation formed at high temperature was promoted by fast-neutron irradiation obviously. Compared with NTDCZSi , fast neutron irradiation accelerated precipitation in CZSi much more. Irradiation defects decompounded and recombined with oxygen impurity and large quantity of nucleation centers were introduced in CZSi bulk during annealing at 1100℃. In Nitrogen atmosphere, more defects were induced in fast neutron irradiated CZSi than in Argon atmosphere.