<s>
The	O
RCA	B-Algorithm
clean	I-Algorithm
is	O
a	O
standard	O
set	O
of	O
wafer	B-Architecture
cleaning	O
steps	O
which	O
need	O
to	O
be	O
performed	O
before	O
high-temperature	O
processing	O
steps	O
(	O
oxidation	O
,	O
diffusion	O
,	O
CVD	B-Algorithm
)	O
of	O
silicon	B-Architecture
wafers	I-Architecture
in	O
semiconductor	O
manufacturing	O
.	O
</s>
<s>
The	O
wafers	B-Architecture
are	O
prepared	O
by	O
soaking	O
them	O
in	O
deionized	O
water	O
.	O
</s>
<s>
The	O
wafers	B-Architecture
are	O
thoroughly	O
rinsed	O
with	O
deionized	O
water	O
between	O
each	O
step	O
.	O
</s>
<s>
Ideally	O
,	O
the	O
steps	O
below	O
are	O
carried	O
out	O
by	O
immersing	O
the	O
wafers	B-Architecture
in	O
solutions	O
prepared	O
in	O
fused	O
silica	O
or	O
fused	O
quartz	O
vessels	O
(	O
borosilicate	O
glassware	O
must	O
not	O
be	O
used	O
,	O
as	O
its	O
impurities	O
leach	O
out	O
and	O
cause	O
contamination	O
)	O
.	O
</s>
<s>
Likewise	O
it	O
is	O
recommended	O
that	O
the	O
chemicals	O
used	O
are	O
electronic	O
grade	O
(	O
or	O
"	O
CMOS	O
grade	O
"	O
)	O
to	O
avoid	O
impurities	O
that	O
will	O
recontaminate	O
the	O
wafer	B-Architecture
.	O
</s>
<s>
The	O
optional	O
second	O
step	O
(	O
for	O
bare	O
silicon	B-Architecture
wafers	I-Architecture
)	O
is	O
a	O
short	O
immersion	O
in	O
a	O
1:100	O
or	O
1:50	O
solution	O
of	O
aqueous	O
HF	O
(	O
hydrofluoric	O
acid	O
)	O
at	O
25°C	O
for	O
about	O
fifteen	O
seconds	O
,	O
in	O
order	O
to	O
remove	O
the	O
thin	O
oxide	O
layer	O
and	O
some	O
fraction	O
of	O
ionic	O
contaminants	O
.	O
</s>
<s>
It	O
also	O
leaves	O
a	O
thin	O
passivating	O
layer	O
on	O
the	O
wafer	B-Architecture
surface	O
,	O
which	O
protects	O
the	O
surface	O
from	O
subsequent	O
contamination	O
(	O
bare	O
exposed	O
silicon	O
is	O
contaminated	O
immediately	O
)	O
.	O
</s>
<s>
Provided	O
the	O
RCA	B-Algorithm
clean	I-Algorithm
is	O
performed	O
with	O
high-purity	O
chemicals	O
and	O
clean	O
glassware	O
,	O
it	O
results	O
in	O
a	O
very	O
clean	O
wafer	B-Architecture
surface	O
while	O
the	O
wafer	B-Architecture
is	O
still	O
submersed	O
in	O
water	O
.	O
</s>
<s>
A	O
variety	O
of	O
procedures	O
can	O
be	O
used	O
to	O
rinse	O
and	O
dry	O
the	O
wafer	B-Architecture
effectively	O
.	O
</s>
<s>
The	O
first	O
step	O
in	O
the	O
ex	O
situ	O
cleaning	O
process	O
is	O
to	O
ultrasonically	O
degrease	O
the	O
wafer	B-Architecture
in	O
trichloroethylene	O
,	O
acetone	O
and	O
methanol	O
.	O
</s>
