Oxygen '96

Early Stages of Oxygen Precipitation in Silicon

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INJECTION ENHANCED REACTIONS OF INTERSTITIAL DEFECTS IN SILICON

B. N. Mukashev, Kh. A. Abdullin and Yu. V. Gorelkinskii

Physical Technical Institute, National Academy of Sciences, 480082, Almaty, Kazakstan

Keywords: defect, silicon, irradiation, selfinterstitial, injection

In this paper we report experimental evidence of strong ionisation effect on the self-interstitials formation and its stability in silicon.

DLTS and TSCAP studies of pulled (CG) and floating-zone-grown (FZ) silicon doped boron or aluminium (=0.2-1 Ohm/cm²) are performed. Samples are irradiated by electrons, protons or alpha-particles at 77 K. Spectra of all proton- and alpha-irradiated samples are revealed E1=E_c-0.39 eV defect state. This is the main defect in these samples in contrast to electron irradiated silicon. It is important to note that E1 defect is stable up to 320-350 K, however under injection conditions it is annealed out at 77 K. The annealing of E1 centres is accompanied by appearance of C_i centres (H1=E_v+0.29 eV), Al_i centres in Si(Al)-FZ and additional H2=E_v+0.13 eV level in CG samples. E1-defect was identified as a selfinterstitial centre [1]. The reversible transition between E1 and H2 defects is occurred: E1 annealing under injection at 77 K increases the concentration of H2 centre and the annealing at 180-200 K transforms H2 into E1. It is supposed that H2 defect belongs to (Si_i -O_i) complex therefore the reaction Si_i+O_i H2 (Si_i -O_i ) explains observed reversible transformation. This result demonstrates that E1 defect migrates at 77 K under injection condition without decomposition.

ESR studies of the CG and FZ samples irradiated at ~80 K were resolved new high intensive spectrum (labelled Si-AA12) with isotropic g=1.9998 (77 K) and ²⁹Si hyperfine (hf) interaction (~45.5 MHz) from one silicon atom. It is also observed unresolved hf interaction (~9.5 MHz) from four equivalent silicon atoms. This centre is detected in FZ immediately after irradiation and in CG silicon after annealing at 180-250 K . The correlation between behaviour of this centre and E1-defect is found: i) both centres are emptied at 140-160 K (but subsequent light illumination is recovered of the line amplitude), ii) thermal annealing is occurred at 320-350 K, iii) ESR signal of Al_i (G18) is appeared after annealing of the AA12 (it is known that G18 was observed in silicon after electron irradiation at 4 K [2]). Tentative model of defect responsible after annealing of the AA12 (It is known that G18 was observed in silicon after electron irradiation at 4 K [2]). Tentative model of defect responsible for the E1-level and AA12 ESR centre are proposed. Effects of ionisation and elastic stopping power of protons, alpha-particles and electrons on the interstitial formation and stabilisation are discussed.

Last modified: Wed Feb 28 09:49:20 GMT 1996 JG