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

identical to the 60 nm SOI series in Figure 6.26b) using 3 keV BF2 and hence the same
observations apply.
Summarising this section, the unusual regrowth of SOI wafers seen with the PAI
As implanted samples is also seen with the PAI BF2 implanted samples. The most
significant feature is the wide a/c interface of up to 14 nm width. Upon continued
annealing this proceeds towards the surface, where there is a tightening of the a/c
interface. The regrowth on the PAI SOI samples appears to be delayed relative to the
rate of regrowth in bulk Si.
Yield (counts per 5 µC)
400
350
300
250
200
150
100
50
a) Bulk, PAI, 3keV BF 2
20 15 10 5 0 20 15 10 5 0 20 15 10 5 0
Si depth (nm) Si depth (nm)
Si depth (nm)
virgin
random
550C 600s
600C 60s
650C 15s
700C 15s
0
68 70 72 74 76 78 80 82 84
b) 60nm SOI, PAI, 3keV BF 2
68 70 72 74 76 78 80 82 84 68 70 72 74 76 78 80 82 84
Energy (keV)
6.4.3.4 88 nm SOI vs. bulk Si, PAI Xe 40 keV 1E14, As 3 keV 2E15
In order to confirm the differences in regrowth behaviour for bulk Si and SOI, a
series of experiments was performed using identical implantations and simultaneous
anneals on bulk Si and 88 nm SOI. Both wafers were pre-amorphised with 40 keV Xe to
a dose of 1E14 cm -2 and implanted with 3 keV As to a fluence of 2E15 cm -2 , conditions
typically used in this thesis. Samples were annealed at 600 °C for different durations.
Figure 6.27 shows results from 88 nm SOI samples (top) and bulk Si samples
(bottom). The SOI samples show the same wider a/c interface as seen with the previous
SOI series. The samples annealed for 50s, 60s, and 65s all have downslopes with similar
gradients. A linear fit through the slopes illustrates this point more clearly. The slope
163
c) 100nm SOI, PAI, 1keV BF 2
Figure 6.26 MEIS energy spectra from BF2 samples a) bulk Si, b) 60 nm SOI, and c) 100 nm
SOI. In all cases the wafers were pre amorphised with 40 keV Xe to a fluence of 1E14 cm -2 .
In a) and b) samples were implanted with 3 keV BF2 and in c) with 1 keV BF2. Samples
were annealed at various temperatures, as indicated.