<s>
Chemical	B-Algorithm
vapor	I-Algorithm
deposition	I-Algorithm
(	O
CVD	O
)	O
is	O
a	O
vacuum	O
deposition	O
method	O
used	O
to	O
produce	O
high	O
quality	O
,	O
and	O
high-performance	O
,	O
solid	O
materials	O
.	O
</s>
<s>
In	O
typical	O
CVD	O
,	O
the	O
wafer	B-Architecture
(	O
substrate	B-Architecture
)	O
is	O
exposed	O
to	O
one	O
or	O
more	O
volatile	O
precursors	O
,	O
which	O
react	O
and/or	O
decompose	O
on	O
the	O
substrate	B-Architecture
surface	O
to	O
produce	O
the	O
desired	O
deposit	O
.	O
</s>
<s>
These	O
materials	O
include	O
:	O
silicon	O
(	O
dioxide	O
,	O
carbide	O
,	O
nitride	O
,	O
oxynitride	O
)	O
,	O
carbon	O
(	O
fiber	O
,	O
nanofibers	O
,	O
nanotubes	O
,	O
diamond	O
and	O
graphene	O
)	O
,	O
fluorocarbons	O
,	O
filaments	O
,	O
tungsten	B-Application
,	O
titanium	O
nitride	O
and	O
various	O
high-κ	B-Algorithm
dielectrics	I-Algorithm
.	O
</s>
<s>
The	O
term	O
chemical	B-Algorithm
vapour	I-Algorithm
deposition	I-Algorithm
was	O
coined	O
1960	O
by	O
John	O
M	O
.	O
Blocher	O
,	O
Jr.	O
who	O
intended	O
to	O
differentiate	O
chemical	O
from	O
physical	O
vapour	B-Algorithm
deposition	I-Algorithm
(	O
PVD	O
)	O
.	O
</s>
<s>
Atmospheric	B-Algorithm
pressure	I-Algorithm
CVD	I-Algorithm
(	O
APCVD	B-Algorithm
)	O
–	O
CVD	O
at	O
atmospheric	O
pressure	O
.	O
</s>
<s>
Low-pressure	O
CVD	O
(	O
LPCVD	B-Algorithm
)	O
–	O
CVD	O
at	O
sub-atmospheric	O
pressures	O
.	O
</s>
<s>
Reduced	O
pressures	O
tend	O
to	O
reduce	O
unwanted	O
gas-phase	O
reactions	O
and	O
improve	O
film	O
uniformity	O
across	O
the	O
wafer	B-Architecture
.	O
</s>
<s>
Ultrahigh	O
vacuum	O
CVD	O
(	O
UHVCVD	B-Algorithm
)	O
–	O
CVD	O
at	O
very	O
low	O
pressure	O
,	O
typically	O
below	O
10−6	O
Pa	O
( ≈10−8	O
torr	O
)	O
.	O
</s>
<s>
Most	O
modern	O
CVD	O
is	O
either	O
LPCVD	B-Algorithm
or	O
UHVCVD	B-Algorithm
.	O
</s>
<s>
Aerosol	O
assisted	O
CVD	O
(	O
AACVD	O
)	O
–	O
CVD	O
in	O
which	O
the	O
precursors	O
are	O
transported	O
to	O
the	O
substrate	B-Architecture
by	O
means	O
of	O
a	O
liquid/gas	O
aerosol	O
,	O
which	O
can	O
be	O
generated	O
ultrasonically	O
.	O
</s>
<s>
The	O
precursor	O
vapors	O
are	O
then	O
transported	O
to	O
the	O
substrate	B-Architecture
as	O
in	O
classical	O
CVD	O
.	O
</s>
<s>
Classified	O
by	O
type	O
of	O
substrate	B-Architecture
heating	O
:	O
</s>
<s>
Hot	O
wall	O
CVD	O
–	O
CVD	O
in	O
which	O
the	O
chamber	O
is	O
heated	O
by	O
an	O
external	O
power	O
source	O
and	O
the	O
substrate	B-Architecture
is	O
heated	O
by	O
radiation	O
from	O
the	O
heated	O
chamber	O
walls	O
.	O
</s>
<s>
Cold	O
wall	O
CVD	O
–	O
CVD	O
in	O
which	O
only	O
the	O
substrate	B-Architecture
is	O
directly	O
heated	O
either	O
by	O
induction	O
or	O
by	O
passing	O
current	O
through	O
the	O
substrate	B-Architecture
itself	O
or	O
a	O
heater	O
in	O
contact	O
with	O
the	O
substrate	B-Architecture
.	O
</s>
<s>
Remote	O
plasma-enhanced	O
CVD	O
(	O
RPECVD	B-Algorithm
)	O
–	O
Similar	O
to	O
PECVD	O
except	O
that	O
the	O
wafer	B-Architecture
substrate	B-Architecture
is	O
not	O
directly	O
in	O
the	O
plasma	O
discharge	O
region	O
.	O
</s>
<s>
Removing	O
the	O
wafer	B-Architecture
from	O
the	O
plasma	O
region	O
allows	O
processing	O
temperatures	O
down	O
to	O
room	O
temperature	O
.	O
</s>
<s>
Low-energy	O
plasma-enhanced	O
chemical	B-Algorithm
vapor	I-Algorithm
deposition	I-Algorithm
(	O
LEPECVD	O
)	O
-	O
CVD	O
employing	O
a	O
high	O
density	O
,	O
low	O
energy	O
plasma	O
to	O
obtain	O
epitaxial	O
deposition	O
of	O
semiconductor	O
materials	O
at	O
high	O
rates	O
and	O
low	O
temperatures	O
.	O
</s>
<s>
Combustion	O
chemical	B-Algorithm
vapor	I-Algorithm
deposition	I-Algorithm
(	O
CCVD	O
)	O
–	O
Combustion	O
Chemical	B-Algorithm
Vapor	I-Algorithm
Deposition	I-Algorithm
or	O
flame	O
pyrolysis	O
is	O
an	O
open-atmosphere	O
,	O
flame-based	O
technique	O
for	O
depositing	O
high-quality	O
thin	O
films	O
and	O
nanomaterials	O
.	O
</s>
<s>
The	O
filament	O
temperature	O
and	O
substrate	B-Architecture
temperature	O
thus	O
are	O
independently	O
controlled	O
,	O
allowing	O
colder	O
temperatures	O
for	O
better	O
absorption	O
rates	O
at	O
the	O
substrate	B-Architecture
and	O
higher	O
temperatures	O
necessary	O
for	O
decomposition	O
of	O
precursors	O
to	O
free	O
radicals	O
at	O
the	O
filament	O
.	O
</s>
<s>
Metalorganic	B-Algorithm
chemical	I-Algorithm
vapor	I-Algorithm
deposition	I-Algorithm
(	O
MOCVD	B-Algorithm
)	O
–	O
This	O
CVD	O
process	O
is	O
based	O
on	O
metalorganic	O
precursors	O
.	O
</s>
<s>
Rapid	B-Algorithm
thermal	I-Algorithm
CVD	I-Algorithm
(	O
RTCVD	B-Algorithm
)	O
–	O
This	O
CVD	O
process	O
uses	O
heating	O
lamps	O
or	O
other	O
methods	O
to	O
rapidly	O
heat	O
the	O
wafer	B-Architecture
substrate	B-Architecture
.	O
</s>
<s>
Heating	O
only	O
the	O
substrate	B-Architecture
rather	O
than	O
the	O
gas	O
or	O
chamber	O
walls	O
helps	O
reduce	O
unwanted	O
gas-phase	O
reactions	O
that	O
can	O
lead	O
to	O
particle	O
formation	O
.	O
</s>
<s>
Laser	B-Algorithm
chemical	I-Algorithm
vapor	I-Algorithm
deposition	I-Algorithm
(	O
LCVD	O
)	O
-	O
This	O
CVD	O
process	O
uses	O
lasers	O
to	O
heat	O
spots	O
or	O
lines	O
on	O
a	O
substrate	B-Architecture
in	O
semiconductor	O
applications	O
.	O
</s>
<s>
CVD	O
is	O
commonly	O
used	O
to	O
deposit	O
conformal	O
films	O
and	O
augment	O
substrate	B-Architecture
surfaces	O
in	O
ways	O
that	O
more	O
traditional	O
surface	O
modification	O
techniques	O
are	O
not	O
capable	O
of	O
.	O
</s>
<s>
Recently	O
scaled	O
up	O
as	O
an	O
integrated	O
cleanroom	O
process	O
depositing	O
large-area	O
substrates	B-Architecture
,	O
the	O
applications	O
for	O
these	O
films	O
are	O
anticipated	O
in	O
gas	O
sensing	O
and	O
low-κ	B-Algorithm
dielectrics	I-Algorithm
.	O
</s>
<s>
This	O
reaction	O
is	O
usually	O
performed	O
in	O
LPCVD	B-Algorithm
systems	O
,	O
with	O
either	O
pure	O
silane	O
feedstock	O
,	O
or	O
a	O
solution	O
of	O
silane	O
with	O
70	O
–	O
80%	O
nitrogen	O
.	O
</s>
<s>
Polysilicon	O
may	O
be	O
grown	O
directly	O
with	O
doping	B-Algorithm
,	O
if	O
gases	O
such	O
as	O
phosphine	O
,	O
arsine	O
or	O
diborane	O
are	O
added	O
to	O
the	O
CVD	O
chamber	O
.	O
</s>
<s>
The	O
choice	O
of	O
source	O
gas	O
depends	O
on	O
the	O
thermal	O
stability	O
of	O
the	O
substrate	B-Architecture
;	O
for	O
instance	O
,	O
aluminium	O
is	O
sensitive	O
to	O
high	O
temperature	O
.	O
</s>
<s>
Any	O
of	O
these	O
reactions	O
may	O
be	O
used	O
in	O
LPCVD	B-Algorithm
,	O
but	O
the	O
silane	O
reaction	O
is	O
also	O
done	O
in	O
APCVD	B-Algorithm
.	O
</s>
<s>
CVD	O
oxide	O
invariably	O
has	O
lower	O
quality	O
than	O
thermal	B-Algorithm
oxide	I-Algorithm
,	O
but	O
thermal	B-Algorithm
oxidation	I-Algorithm
can	O
only	O
be	O
used	O
in	O
the	O
earliest	O
stages	O
of	O
IC	O
manufacturing	O
.	O
</s>
<s>
Oxide	O
may	O
also	O
be	O
grown	O
with	O
impurities	O
(	O
alloying	O
or	O
"	O
doping	B-Algorithm
"	O
)	O
.	O
</s>
<s>
Silicon	O
nitride	O
deposited	O
by	O
LPCVD	B-Algorithm
contains	O
up	O
to	O
8%	O
hydrogen	O
.	O
</s>
<s>
Tungsten	B-Application
CVD	O
,	O
used	O
for	O
forming	O
conductive	O
contacts	O
,	O
vias	O
,	O
and	O
plugs	O
on	O
a	O
semiconductor	O
device	O
,	O
is	O
achieved	O
from	O
tungsten	B-Application
hexafluoride	O
(	O
WF6	O
)	O
,	O
which	O
may	O
be	O
deposited	O
in	O
two	O
ways	O
:	O
</s>
<s>
Mo	O
,	O
Ta	O
and	O
Ti	O
are	O
deposited	O
by	O
LPCVD	B-Algorithm
,	O
from	O
their	O
pentachlorides	O
.	O
</s>
<s>
Nickel	O
,	O
molybdenum	O
,	O
and	O
tungsten	B-Application
can	O
be	O
deposited	O
at	O
low	O
temperatures	O
from	O
their	O
carbonyl	O
precursors	O
.	O
</s>
<s>
Although	O
methane	O
is	O
the	O
most	O
popular	O
carbon	O
source	O
,	O
hydrogen	O
is	O
required	O
during	O
the	O
preparation	O
process	O
to	O
promote	O
carbon	O
deposition	O
on	O
the	O
substrate	B-Architecture
.	O
</s>
<s>
The	O
direct	O
growth	O
of	O
high-quality	O
,	O
large	O
single-crystalline	O
domains	O
of	O
graphene	O
on	O
a	O
dielectric	O
substrate	B-Architecture
is	O
of	O
vital	O
importance	O
for	O
applications	O
in	O
electronics	O
and	O
optoelectronics	O
.	O
</s>
<s>
Combining	O
the	O
advantages	O
of	O
both	O
catalytic	O
CVD	O
and	O
the	O
ultra-flat	O
dielectric	O
substrate	B-Architecture
,	O
gaseous	O
catalyst-assisted	O
CVD	O
paves	O
the	O
way	O
for	O
synthesizing	O
high-quality	O
graphene	O
for	O
device	O
applications	O
while	O
avoiding	O
the	O
transfer	O
process	O
.	O
</s>
<s>
Most	O
systems	O
use	O
LPCVD	B-Algorithm
with	O
pressures	O
ranging	O
from	O
1	O
to	O
1500	O
Pa	O
.	O
</s>
<s>
However	O
,	O
some	O
still	O
use	O
APCVD	B-Algorithm
.	O
</s>
<s>
Low	O
pressures	O
are	O
used	O
more	O
commonly	O
as	O
they	O
help	O
prevent	O
unwanted	O
reactions	O
and	O
produce	O
more	O
uniform	O
thickness	O
of	O
deposition	O
on	O
the	O
substrate	B-Architecture
.	O
</s>
<s>
These	O
gases	O
act	O
as	O
a	O
carrier	O
,	O
enhancing	O
surface	O
reaction	O
and	O
improving	O
reaction	O
rate	O
,	O
thereby	O
increasing	O
deposition	O
of	O
graphene	O
onto	O
the	O
substrate	B-Architecture
.	O
</s>
<s>
The	O
study	O
was	O
carried	O
out	O
in	O
a	O
home-built	O
vertical	O
cold	O
wall	O
system	O
utilizing	O
resistive	O
heating	O
by	O
passing	O
direct	O
current	O
through	O
the	O
substrate	B-Architecture
.	O
</s>
<s>
CVD	O
can	O
be	O
used	O
to	O
produce	O
a	O
synthetic	O
diamond	O
by	O
creating	O
the	O
circumstances	O
necessary	O
for	O
carbon	O
atoms	O
in	O
a	O
gas	O
to	O
settle	O
on	O
a	O
substrate	B-Architecture
in	O
crystalline	O
form	O
.	O
</s>
<s>
CVD	O
diamond	O
growth	O
typically	O
occurs	O
under	O
low	O
pressure	O
(	O
1	O
–	O
27	O
kPa	O
;	O
0.145	O
–	O
3.926	O
psi	O
;	O
7.5	O
–	O
203	O
Torr	O
)	O
and	O
involves	O
feeding	O
varying	O
amounts	O
of	O
gases	O
into	O
a	O
chamber	O
,	O
energizing	O
them	O
and	O
providing	O
conditions	O
for	O
diamond	O
growth	O
on	O
the	O
substrate	B-Architecture
.	O
</s>
<s>
Using	O
CVD	O
,	O
films	O
of	O
diamond	O
can	O
be	O
grown	O
over	O
large	O
areas	O
of	O
substrate	B-Architecture
with	O
control	O
over	O
the	O
properties	O
of	O
the	O
diamond	O
produced	O
.	O
</s>
<s>
The	O
growth	O
of	O
diamond	O
directly	O
on	O
a	O
substrate	B-Architecture
allows	O
the	O
addition	O
of	O
many	O
of	O
diamond	O
's	O
important	O
qualities	O
to	O
other	O
materials	O
.	O
</s>
<s>
In	O
each	O
case	O
the	O
diamond	O
growth	O
must	O
be	O
carefully	O
done	O
to	O
achieve	O
the	O
necessary	O
adhesion	O
onto	O
the	O
substrate	B-Architecture
.	O
</s>
<s>
Diamond	O
's	O
very	O
high	O
scratch	O
resistance	O
and	O
thermal	O
conductivity	O
,	O
combined	O
with	O
a	O
lower	O
coefficient	O
of	O
thermal	O
expansion	O
than	O
Pyrex	B-Application
glass	O
,	O
a	O
coefficient	O
of	O
friction	O
close	O
to	O
that	O
of	O
Teflon	O
(	O
polytetrafluoroethylene	O
)	O
and	O
strong	O
lipophilicity	O
would	O
make	O
it	O
a	O
nearly	O
ideal	O
non-stick	O
coating	O
for	O
cookware	O
if	O
large	O
substrate	B-Architecture
areas	O
could	O
be	O
coated	O
economically	O
.	O
</s>
<s>
Consisting	O
of	O
an	O
alloy	B-Application
of	O
CdTe	O
and	O
HgTe	O
,	O
this	O
material	O
can	O
be	O
prepared	O
from	O
the	O
dimethyl	O
derivatives	O
of	O
the	O
respective	O
elements	O
.	O
</s>
