Damage formation and annealing studies of low energy ion implants ...

Figure 3.11 Relationship between implantation dose and
annealing, on the type of defects formed. From (61).
The driving force for this Ostwald ripening process is the decrease in formation
energy. Interstitials to di-interstitials have an energy of formation of 1.3 eV. The
formation of clusters tends towards 0.8 eV. {113}’s have an energy of formation of 0.65
eV, and dislocation loops have an energy of formation of 0.027 eV (57).
3.4.3 Bubbles
Bubbles can be formed in Si. This section briefly mentions implantation
conditions that can lead to bubble formation, relevant to these studies, i.e. with BF2 and
noble gas implants. At high BF2 doses such as 1 × 10 16 cm -2 , F bubble formation may
occur upon annealing. During SPER these bubbles are swept ahead of the advancing
interface. Bubble size increases for higher anneal temperatures (47, 48). At lower
implant BF2 doses that still result in amorphisation (5×10 14 cm -2 ), bubble formation was
not seen (46). Previous implantation and annealing studies of noble gas ion implantation
into Si and metals have shown that implanted ions tend to agglomerate in clusters or
form bubbles depending on the implant dose (62-65). For doses above 6×10 15 cm -2 , Ar
bubbles are formed during implantation and grow upon annealing. For lower doses
bubble formation occurs during annealing (63). For Kr bubble formation does not occur
during implantation but during SPER at temperatures from 550 °C upwards (64). Xe,
similarly, has been shown to form bubbles in Si during annealing (65).
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