Damage accumulation in Si crystal during ion implantation at elevated temperatures: Evidence of chemical effects

Damage in Si induced by irradiation with various light/medium mass ions at elevated temperatures and high doses (≥3×10¹⁶ cm^-2) was studied using Rutherford backscattering spectroscopy, cross-section transmission electron microscopy, and high resolution x-ray diffraction. The results obtained have shown that there is a marked variation in the damage accumulation for different ion species. For O⁺ and N⁺ ions a distinct layer with a low level of damage presenting negative strain is formed at the surface. It has been found that the magnitude of the strain does not correlate with the energy deposited in the collision cascades. In the cases of Ne⁺ and Mg⁺ implantation, a low damage accumulation occurs near the surface but no negative strain is formed. In contrast to the N⁺ and O⁺ cases, with the increase of the Ne⁺ or Mg⁺ dose (> 1×10¹⁷ cm^-2) the damage profile stretches almost to the crystal surface. It is proposed that in addition to the mechanism of spatial separation of Frenkel pairs taking place in the collision cascades, the ability of the implanted ions to form precipitates and complexes with Si atoms noticeably influences the damage formation during implantation at elevated temperatures.