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

As concentration (at/cm 3 )
1E22
1E21
1E20
1E19
1E18
a)
600°C 10s
650°C 10s
700°C 10s
b)
0 10 20 30
Depth (nm)
A direct comparison of the MEIS and SIMS depth profiles for these samples is
shown in Figure 6.17 using the same depth scales for a) 600 °C, b) 650 °C and c)
700 °C. The MEIS spectra have been converted into As concentration profiles to enable
proper comparison with the SIMS profiles. As previously mentioned SIMS has some
inherent problems in calibration of the first couple of nanometres in terms of depth and
concentration, which does mean that the SIMS results have limited accuracy and this
must always be born in mind. MEIS (in the double alignment mode) is sensitive only to
non substitutional As atoms. SIMS however sees all of the As, and so the substitutional
fraction can be inferred.
In Figure 6.17a) the profiles for the sample annealed at 600 °C for 10s is given.
From the MEIS results in Figure 6.15 it can be seen that for this sample there has been
some regrowth at a depth of 8 – 10 nm (As peak), including a small amount of
segregation visible between (5 – 6 nm) and only a small amount of As has taken up
substitutional positions in the regrown layers (8 – 10 nm). In view of this, the MEIS and
SIMS profiles would be expected to be similar, as is the case. The SIMS profile
contains some extra As compared to MEIS in the region of 8-10 nm, at a depth where
there is some substitutional As. Extra As observed in the SIMS profile in the region of
0 - 4 nm is likely to be caused by inaccuracies in the SIMS calibration.
148
600°C 10s
650°C 10s
700°C 10s
5 10
0
15
4x10 21
3x10 21
2x10 21
1x10 21
Figure 6.16 0.5 keV Cs + SIMS As depth profiles for the 3 keV implanted samples annealed
for 10s at 600 °C, 650 °C and 700 °C.
As concentration (at/cm 3 )