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

ate. Samples were annealed at temperatures of 550 °C, 600 °C and 650 °C, respectively,
for different durations and several higher temperature anneals were carried out.
The MEIS energy spectra for samples annealed at 550 °C for 200 s, 500 s and
600 s are shown in Figure 6.25a). For all samples the regrowth is clearly not “standard”
SPER as seen on bulk Si samples. The back edge of the Si damage peaks is stretched
and distributed over a greater depth than would be expected for standard layer-by-layer
SPER, even accounting for energy straggling. For example Figure 6.24 is typical for a
sharp amorphous crystalline interface. The broad amorphous / crystalline interface, of
~13 nm, is most pronounced in the sample annealed for 600s, where a lower
dechannelling level and less overlap with the O peak allows more of the a/c interface
profile to be visible. This broad a/c interface profile is unusual and has not been
observed in our previous MEIS studies on bulk Si (4, 5). There is no single clearly
definable depth for the location of the amorphous / crystalline interface.
The As profiles have not changed compared to the as-implanted profile in Figure
6.25 following any of the anneals at 550 °C. For the sample annealed for 200s this
should be expected, regrowth has not passed the depth of the As. For the sample
annealed for 500s, again this is not too surprising. Regrowth has not come closer to the
surface than 12 nm, which is close to the depth of the end of the As profile. For the
sample annealed for 600s however, clearly some Si recrystallisation has occurred at
depths between 6 and 14 nm but the As present at those depths has not taken up
substitutional positions or become segregated. This behaviour has not been seen with
the bulk Si samples.
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