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

The higher temperature anneals carried out at 700 °C for 15s and 1050 °C spike
anneal, shown in Figure 6.25d) with their faster regrowth rates produced a fully regrown
layer, with less As visible in the regrown layer and hence a clear segregated peak.
In summary of these results, the wide amorphous / crystalline transition regions
observed in the MEIS spectra following anneals where regrowth is not completed are
unique for SOI. The continued visibility of the As in the regrown layer, typical for the
regrowth of SOI pre-amorphised samples, is also an unusual feature.
6.4.3.3 Bulk Si, 60, 100 nm SOI, PAI, 3 and 1 keV BF2
Experiments similar to the ones reported above were carried out using BF2
implants. Samples were produced from bulk Si, 60 nm, and 100 nm SOI wafers,
respectively. All samples were pre-amorphised with 40 keV Xe to a dose of 1E14
ions/cm 2 , and implanted with 1 or 3 keV BF2 + to a dose of 7E14 ions/cm 2 .
MEIS results for the 3 keV BF2 implants into bulk Si are shown in Figure 6.26a)
for anneals at 550 °C for 600s and at 600 °C for 60s. For both samples, the regrowth has
proceeded in the conventional SPER manner as is usual for bulk Si. There is no wide
transition layer from amorphous to crystalline. The anneals have not produced complete
regrowth, since there remains a ~ 4 nm wide Si surface peak after the 550 °C anneal and
a ~ 3 nm wide Si surface peak after the 600 °C anneal. The growth of the oxide layer
thickness only partially accounts for the width of these layers.
MEIS results for 60 nm SOI samples using identical implant conditions are
shown in Figure 6.26b), the only difference with this set of samples is the wafer
material, i.e. SOI. Si damage profiles with wide a/c interfaces similar to those in the PAI
As implanted samples (section 6.4.3.2) are also seen with these samples. The sample
annealed at 550 °C for 600 s has a very broad transition from crystalline to amorphous
Si taking place over a depth of ~ 14 nm. The sample annealed at 600 °C for 60 s also
has high level of residual damage at a depth from 6 to 16 nm, behind a 6 nm wide
highly damaged / amorphous surface peak. The samples annealed at 650 °C and 700 °C
for 15 s both show good regrowth. This is in contrast to the As implanted sample
annealed at 650 °C for 15s, shown in 6.25c), which is not yet fully regrown, attributed
to the effect of the high As concentration slowing down the regrowth.
Lastly the 100 nm SOI wafer was pre-amorphised and then implanted with
1 keV BF2 to a dose of 7E14 ions/cm 2 . An equivalent 3 keV BF2 implanted sample was
not available. It is not likely that the different BF2 energy will cause a fundamentally
different behaviour. The results are shown in Figure 6.26c) and they prove almost
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