<s>
Vapour	B-Algorithm
phase	I-Algorithm
decomposition	I-Algorithm
(	O
VPD	O
)	O
is	O
a	O
method	O
used	O
in	O
the	O
semiconductor	O
industry	O
to	O
improve	O
the	O
sensitivity	O
of	O
total-reflection	O
x-ray	O
fluorescence	O
spectroscopy	O
by	O
changing	O
the	O
contaminant	O
from	O
a	O
thin	O
layer	O
(	O
which	O
has	O
an	O
angle-dependent	O
fluorescence	O
intensity	O
in	O
the	O
TXRF-domain	O
)	O
to	O
a	O
granular	O
residue	O
.	O
</s>
<s>
In	O
VPD	O
,	O
the	O
surface	O
of	O
the	O
wafer	B-Architecture
is	O
exposed	O
to	O
hydrofluoric	O
acid	O
vapour	O
,	O
which	O
causes	O
the	O
surface	O
oxide	O
to	O
dissolve	O
together	O
with	O
the	O
impurity	O
metals	O
.	O
</s>
<s>
To	O
improve	O
the	O
range	O
of	O
elemental	O
impurities	O
and	O
lower	O
detection	O
limits	O
,	O
the	O
acid	O
droplets	O
obtained	O
from	O
the	O
silicon	B-Architecture
wafers	I-Architecture
are	O
analyzed	O
by	O
ICP-MS	O
(	O
Inductively	O
coupled	O
plasma	O
mass	O
spectrometry	O
)	O
.	O
</s>
<s>
This	O
technique	O
,	O
VPD	O
ICP-MS	O
provides	O
accurate	O
measurement	O
of	O
up	O
to	O
60	O
elements	O
and	O
detection	O
limits	O
of	O
in	O
the	O
range	O
of	O
1E6-E10	O
atoms/sq.cm	O
on	O
the	O
silicon	B-Architecture
wafer	I-Architecture
.	O
</s>
<s>
One	O
related	O
technique	O
is	O
VPD-DC	O
(	O
vapour	O
phase	O
decomposition-droplet	O
collection	O
)	O
,	O
where	O
the	O
wafer	B-Architecture
is	O
scanned	O
with	O
a	O
droplet	O
that	O
collects	O
the	O
metal	O
ions	O
that	O
were	O
dissolved	O
in	O
the	O
decomposition	O
step	O
.	O
</s>
<s>
This	O
procedure	O
affords	O
better	O
limits	O
of	O
detection	O
when	O
applying	O
AAS	O
in	O
order	O
to	O
detect	O
metal	O
impurities	O
of	O
very	O
small	O
concentrations	O
on	O
wafer	B-Architecture
surfaces	O
.	O
</s>
