<s>
In	O
semiconductor	B-Architecture
fabrication	I-Architecture
,	O
a	O
resist	O
is	O
a	O
thin	O
layer	O
used	O
to	O
transfer	O
a	O
circuit	O
pattern	O
to	O
the	O
semiconductor	O
substrate	O
which	O
it	O
is	O
deposited	O
upon	O
.	O
</s>
<s>
A	O
resist	O
can	O
be	O
patterned	O
via	O
lithography	B-Algorithm
to	O
form	O
a	O
(	O
sub	O
)	O
micrometer-scale	O
,	O
temporary	O
mask	O
that	O
protects	O
selected	O
areas	O
of	O
the	O
underlying	O
substrate	O
during	O
subsequent	O
processing	O
steps	O
.	O
</s>
<s>
Resists	O
are	O
generally	O
proprietary	O
mixtures	O
of	O
a	O
polymer	B-Language
or	O
its	O
precursor	O
and	O
other	O
small	O
molecules	O
(	O
e.g.	O
</s>
<s>
photoacid	O
generators	O
)	O
that	O
have	O
been	O
specially	O
formulated	O
for	O
a	O
given	O
lithography	B-Algorithm
technology	O
.	O
</s>
<s>
Resists	O
used	O
during	O
photolithography	B-Algorithm
are	O
called	O
photoresists	O
.	O
</s>
<s>
The	O
patterning	O
steps	O
,	O
or	O
lithography	B-Algorithm
,	O
define	O
the	O
function	O
of	O
the	O
device	O
and	O
the	O
density	O
of	O
its	O
components	O
.	O
</s>
<s>
The	O
metal	O
patterns	O
define	O
multiple	O
electrical	O
circuits	O
that	O
are	O
used	O
to	O
connect	O
the	O
microchip	O
's	O
transistors	B-Application
to	O
one	O
another	O
and	O
ultimately	O
to	O
external	O
devices	O
via	O
the	O
chip	O
's	O
pins	O
.	O
</s>
<s>
The	O
most	O
common	O
patterning	O
method	O
used	O
by	O
the	O
semiconductor	O
device	O
industry	O
is	O
photolithography	B-Algorithm
--	O
patterning	O
using	O
light	O
.	O
</s>
<s>
In	O
this	O
process	O
,	O
the	O
substrate	O
of	O
interest	O
is	O
coated	O
with	O
photosensitive	O
resist	O
and	O
irradiated	O
with	O
short-wavelength	O
light	O
projected	O
through	O
a	O
photomask	B-Algorithm
,	O
which	O
is	O
a	O
specially	O
prepared	O
stencil	B-Algorithm
formed	O
of	O
opaque	O
and	O
transparent	O
regions	O
-	O
usually	O
a	O
quartz	B-General_Concept
substrate	O
with	O
a	O
patterned	O
chromium	B-Language
layer	O
.	O
</s>
<s>
The	O
shadow	O
of	O
opaque	O
regions	O
in	O
the	O
photomask	B-Algorithm
forms	O
a	O
submicrometer-scale	O
pattern	O
of	O
dark	O
and	O
illuminated	O
regions	O
in	O
the	O
resist	O
layer	O
--	O
the	O
areal	O
image	O
.	O
</s>
<s>
This	O
pattern	O
can	O
be	O
used	O
as	O
a	O
stencil	B-Algorithm
in	O
the	O
next	O
process	O
step	O
.	O
</s>
<s>
during	O
Microelectromechanical	B-Architecture
systems	I-Architecture
fabrication	B-Architecture
)	O
,	O
the	O
patterned	O
resist	O
layer	O
may	O
be	O
incorporated	O
in	O
the	O
final	O
product	O
.	O
</s>
<s>
Many	O
photolithography	B-Algorithm
and	O
processing	O
cycles	O
may	O
be	O
performed	O
to	O
create	O
complex	O
devices	O
.	O
</s>
<s>
This	O
is	O
the	O
basis	O
of	O
electron-beam	B-Architecture
direct-write	I-Architecture
lithography	I-Architecture
.	O
</s>
<s>
Several	O
materials	O
may	O
be	O
deposited	O
or	O
patterned	O
directly	O
using	O
techniques	O
like	O
soft	B-Algorithm
lithography	I-Algorithm
,	O
Dip-Pen	O
Nanolithography	B-Algorithm
,	O
evaporation	O
through	O
a	O
shadow	O
mask	O
or	O
stencil	B-Algorithm
.	O
</s>
<s>
(	O
a	O
)	O
via	O
exposure	O
to	O
ultraviolet	O
light	O
through	O
a	O
photomask	B-Algorithm
with	O
opaque	O
and	O
transparent	O
regions	O
or	O
(	O
b	O
)	O
by	O
direct	O
writing	O
using	O
a	O
laser	O
beam	O
or	O
electron	O
beam	O
.	O
</s>
