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

Following annealing it was observed that at the lowest temperatures used, the
regrowth was marginally slower in the Epi silicon than the Cz silicon. With the 550 °C
Epi sample the depth of the half height of the silicon damage peak is at 7.3 nm, while
the Cz sample is ~ 0.4 nm closer to the surface. This behaviour is replicated in the
position of the half height of the back edge of the arsenic peaks, which are at the same
depth as the corresponding silicon damage layer. A small amount of segregation has
occurred, as shown by the additional build-up of arsenic in front of the as-implanted
peak, (at a depth of 4 to 7 nm). The 600 °C 20 s anneal also does not produce a fully
regrown layer. Here the difference between Cz and Epi silicon appears to be the starkest,
with the Epi sample regrown to a depth of 6.4 nm and the Cz has regrown by a further
0.9 nm to a depth of 5.5 nm. This is repeated in a similar fashion for the back edges of
the arsenic peak, which appears to be contained within the depth of the silicon damage
layer. The higher temperature anneals at 650 °C and 700 °C produce a much better
crystal regrowth. All have a silicon surface peak extending to a depth of 3.5 – 3.8 nm.
Again the Epi samples are marginally thicker than Cz ones.
6.3.3.2 X-ray Techniques
Both the Epi and Cz sample series were studied using combined x-ray scattering
methods (18-20). A summary of GI-DXS and SR findings reported in (19, 20), is given.
GI-DXS results showed that the EOR region contained point defects, and that the depth
of the EOR region is the same for all samples. The signal from the EOR region was
weakest in the 700 °C annealed sample. The segregated As peak provides enough
electron density to produce an oscillation in the SR spectra for the 650 °C and 700 °C
samples in the same way as for the RTA samples described in section 6.2.3.3. However
this contrast is weaker than for the spike annealed sample, and does not provide any
new information. The results are not presented here.
XRD results provide an interesting comparison with MEIS. Before this
comparison is made in section 6.3.3.3, the XRD results are briefly summarised. XRD
measurements have been carried out on the (004) Bragg peak for both the Epi and Cz
series. The two series give very similar results, as was also observed with MEIS. Only
the data for the Epi series is shown in Figure 6.20. They show an oscillation with a
period getting shorter with increasing annealing temperature. The slope of the intensity
is associated with disorder and/or roughness at the a/c interface, while the oscillation is
related to the interference between this interface and the EOR defects region.
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