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

Abstract

Damage in Si induced by irradiation with various light/medium mass ions at elevated temperatures and high doses (у3ϫ10 16 cm Ϫ2 ) 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 ϩ and N ϩ 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 ϩ and Mg ϩ implantation, a low damage accumulation occurs near the surface but no negative strain is formed. In contrast to the N ϩ and O ϩ cases, with the increase of the Ne ϩ or Mg ϩ dose (Ͼ1ϫ10 17 cm Ϫ2 ) 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.

Amorphization/recrystallization of buried amorphous silicon layer induced by oxygen ion implantation

“…The thickness of the a-Si layer is approximately 300 nm. In accordance with previous studies, 19,20 the near surface region ͑until the depth of ϳ150 nm in the present case͒ is apparently defect free after a high temperature implantation. In fact, this region accumulates a high density of vacancy clusters as a result of the ion implantation conditions, leading to the appearance of a localized mechanical strain in the crystal lattice.…”

On the microstructure of Si coimplanted with H+ and He+ ions at moderate energies

“…Self-interstitial atoms introduce tensile strain in the lattice, 21 and, in opposition, vacancies generate compressive strain. 20 For medium and heavy ions implantation, such individual effects are clearer due to the reasonable spatial separation between vacancy, ion, and interstitial profiles. [20][21][22] In the case of light ions as H + and He + , the closer location of damage and ion profiles renders a more intricate system.…”

“…The physical origin of the intrinsic strain is complex and depends on the implanted specie, its chemical-physical interaction with the matrix and with the created lattice damage. 20 Generally, in addition to the implanted atoms, the collision cascade produced by the incident ions mostly creates vacancies and self-interstitials in the matrix. Self-interstitial atoms introduce tensile strain in the lattice, 21 and, in opposition, vacancies generate compressive strain.…”

Strain development and damage accumulation during neon ion implantation into silicon at elevated temperatures

“…In contrast to c-Si samples implanted with O ϩ , N ϩ , or Si ϩ at elevated temperatures, where a negatively strained layer is formed near the surface, 3,5,14 in the samples implanted with Ne ϩ only a positive strain is observed. In the case of Ne ϩ implantation, the ballistic mechanisms which produce an excess concentration of vacancies near the sample surface also take place.…”

“…14 In the case of high temperature O ϩ implantation the damage profile practically does not change with the increase of the O ϩ dose from 0.3 to 2.0ϫ10 17 cm Ϫ2 , indicating saturation of the damage accumulation. In contrast to that, such saturation of the damage accumulation does not occur in the Ne ϩ implanted samples since a significant broadening of the damage profile, mostly towards the surface, is observed with the increase of the dose ͑see Fig.…”