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

approximately 200 nm wide. Implants have been carried out similar to the ones used
previously. Annealing conditions used have been predominantly in the low temperature
range (550 °C to 700 °C) in order to capture intermediate stages of regrowth, rather than
using higher anneal temperatures typical of device production for which the regrowth
occurs too quickly. It will be seen that for PAI implant energies which are sufficiently
high for some damage to extend to the buried oxide (BOX) interface, regrowth is
different from the normally layer-by-layer regrowth, probably through changed seed
conditions at the start of the regrowth.
6.4.2 Experimental
A range of samples were produced to compare the regrowth of 60 nm, 88 nm
and 100 nm SOI wafers with bulk Si wafers. Implantation was carried out using
conditions typical for As and BF2 extension implants into crystalline and Xe preamorphised
wafers, (3 keV As, to fluences of 2E15 cm -2 and 1E15 cm -2 , 3 keV and 1
keV BF2 implants to a fluence of 7E14cm -2 ). For the PAI samples 40 keV Xe was
implanted to a fluence of 1E14cm -2 . Anneals were carried out at the University of
Salford. MEIS was carried out with 100 keV He + and the samples were aligned along
the [īīı] direction and the analyser positioned to record the [332] and [111] blocking
directions. The results from the [111] direction are presented.
6.4.3 Results
Results of several experimental series are presented in the next few subsections
and an overall discussion, based on all the results, is given in section 6.4.4.
6.4.3.1 No – PAI samples
MEIS energy spectra for samples implanted with 3 keV As ions to a dose of
2E15 ions/cm 2 into crystalline bulk Si, 60 nm SOI and 100 nm SOI, respectively, are
shown in Figure 6.24, for as-implanted samples and following annealing at 600 °C for
30 s. Also included in the figure is a spectrum from a virgin Si sample and a random
spectrum taken from an amorphous Si sample. Depth scales have been added to the
figure to give an indication of the depth of scattering from As, Si and O atoms,
respectively. The implantation, as is typical, produces an ~ 11 nm wide amorphous layer.
For the as-implanted samples there are no major differences observed between the
different wafer types. Following annealing all samples have undergone SPER of part of
the amorphous layers, with the surface damage peaks extending to a depth of ~ 7 nm
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