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

underneath the SiO2 layer, iii) it appears that some suboxides exists around the
segregated As peak.
yield (counts per 5 µC)
400
350
300
250
200
150
100
50
4000
350
300
250
200
150
100
50
a) as-implanted b) 600C 10s
c) 600C 60s d) 600C 120s
0
0 2 4 6 8 10 12 14
Depth (nm)
SIMS analysis was carried out at with 0.5 keV and 0.25 keV Cs + primary beams
and no appreciable difference was observed between the two energies. The SIMS
profiles for some of the annealed samples are shown in Figure 6.13a) using a
logarithmic concentration scale and in Figure 6.13b) using a linear concentration scale.
Note that the depth range is different in the two figures. A profile from an equivalent asimplanted
sample is included in Figure 6.13a). Only minor differences are observed
between the profiles of the annealed samples and this as-implanted case beyond the near
surface, i.e. deeper diffusion does not occur. The lack of diffusion to greater depths is
crucially important in determining the usefulness of this type of annealing for the
production of shallow junctions. Figure 6.13 shows clearly that the As profiles are
changed little upon annealing for concentrations below ~2E21 cm -3 . This concentration
is of the order of the maximum solid solubility (21, 22). However clear changes for
concentrations higher than 2E21 cm -3 do occur, which are most clearly seen in Figure
6.13b) which has a reduced depth range. SIMS profiles agree with the trend of the
MEIS results in terms of the segregation of As that cannot be accommodated in the
144
As
Si
O
2 4 6 8 10 12 14
Figure 6.12 As, Si and O depth profiles for the 3 keV As implanted samples, as-implanted
and following 600 °C annealing for different durations.