<s>
Buffered	B-Algorithm
oxide	I-Algorithm
etch	I-Algorithm
(	O
BOE	O
)	O
,	O
also	O
known	O
as	O
buffered	B-Algorithm
HF	I-Algorithm
or	O
BHF	O
,	O
is	O
a	O
wet	O
etchant	B-Algorithm
used	O
in	O
microfabrication	O
.	O
</s>
<s>
Its	O
primary	O
use	O
is	O
in	O
etching	B-Algorithm
thin	O
films	O
of	O
silicon	O
dioxide	O
(	O
SiO2	O
)	O
or	O
silicon	O
nitride	O
(	O
Si3N4	O
)	O
.	O
</s>
<s>
Buffered	B-Algorithm
oxide	I-Algorithm
etch	I-Algorithm
is	O
commonly	O
used	O
for	O
more	O
controllable	O
etching	B-Algorithm
.	O
</s>
<s>
A	O
common	O
buffered	B-Algorithm
oxide	I-Algorithm
etch	I-Algorithm
solution	O
comprises	O
a	O
6:1	O
volume	O
ratio	O
of	O
40%	O
NH4F	O
in	O
water	O
to	O
49%	O
HF	O
in	O
water	O
.	O
</s>
<s>
This	O
solution	O
will	O
etch	O
thermally	B-Algorithm
grown	I-Algorithm
oxide	I-Algorithm
at	O
approximately	O
2	O
nanometres	O
per	O
second	O
at	O
25	O
degrees	O
Celsius	O
.	O
</s>
<s>
Temperature	O
can	O
be	O
increased	O
to	O
raise	O
the	O
etching	B-Algorithm
rate	O
.	O
</s>
<s>
Continuous	O
stirring	O
of	O
the	O
solution	O
during	O
the	O
etching	B-Algorithm
process	O
helps	O
to	O
have	O
a	O
more	O
homogeneous	O
solution	O
,	O
which	O
may	O
etch	O
more	O
uniformly	O
by	O
removing	O
etched	O
material	O
from	O
the	O
surface	O
.	O
</s>
