Oxford-100-Manual.pdf - 第159页
System Manual Oxford Instruments Plasma Technology Plasma lab Endpoint trace - (derivative, less than) Time ) process ENOof Overetch time :~( , : Endpoint I capture time Derivative crosses its endpoint threshold level. E…
Plasma
lab
Oxford
Instruments Plasma Technology
System Manual
3.2.10.4
Typical
OES
endpoint
wavelengths
Material
etched Gas species
Wavelength
Rise/fall
at
endpoint
detected
nm
Si
F 704
Rise
Si
SiF
440, 777 Fall
Si
SiCI
287
Fall
Si02 F 704
Rise
Si02
CO
483
Fall
Resist,
polyimide
0
843
Rise
Resist,
polyimide
CO
483 Fall
Resist,
polyimide
OH
309
Fall
Resist,
polyimide
H 656
Fall
Si3N4
N2
337
Fall
Si3N4
CN
387
Fall
Si3N4 N 674 Fall
W F 704
Rise
AI
AI
391,394,396
Fall
3.2.10.5
Endpoint
algorithm
examples
Endpoint
trace
- (signal,
falling)
%
level
END
of
process
Normalisation
level
Threshold
level
Signal
crosses
its
Signal
endpoint
threshold
level.
Endpoint
capture
timer
l
~-
--I
.......
--------------------------------------------------------~---J-------------t----
I
',-
~
I
_______ , ,
__
" :
_·_-::··_.tc,
=.,_~~_-.::_~~.j
_
Normalisation
time
)
Endpoint
closed
time
(no
false
endpoint
can
be
found)
:~(
):Time
:
Endpoint
Overetch
I capture
time
I
time
Process
Information
(Information
contained
in this
document
is
confidential)
Issue
1:
December 03 Page 16
of
30 Printed: 08 January 2006 09:37
System
Manual
Oxford
Instruments
Plasma Technology
Plasma
lab
Endpoint
trace
-
(derivative,
less
than)
Time
)
process
ENOof
Overetch
time
:~(
,
:
Endpoint
I
capture
time
Derivative
crosses
its
endpoint
threshold
level.
Endpoint
captLR'e
timer
started.
Sigmd
d
Endpoint
closed
time
(nofals8
endpoint
can
be
found)
Derivative
\
\
:
\ i
~
i
/~'"
i
:0:~~~::::/~:::::::~---~";:'ir~z-"
\~
:
,
,
,
,
,
,
,
,
,
Normalisation
time
%
level
+/-
derivative
3.2.11
Gas
calibration
factors
See
the
MKS OEM manual
for
details
of
gas correction factors. However,
it
is
worth
pointing
out
that
for
certain gases (e.g.
H2
or
He)
it
is
recommended
that
the
MFC
is
calibrated
for
that
particular
gas, since
they
have very
different
gas properties compared
to
other
gases, and hence
the
errors on calibrations
factors
is
large.
3.2.12
Exhaust
emissions
The gas
emitted
by a plasma etch process
will
be mostly made
up
of
the
input
gases.
However,
there
will
be a small
but
significant
component
of
etch
or
plasma by-products
(say
up
to
-10%
in an
RIE
tool,
possibly
more
for
ICP).
The exact
amounts
will
depend
on process
type
and conditions. These can be any
combination
of
etch gas
material
and etched material.
For example:
Si
+
CF
4
=
SiFx,
CFx,
Fetc
Si0
2
+
CHF
3
=
SiFx,
COx,
CFx,
F,
HF,
CHx,
SiOFx
etc
Resist
+ O
2
=
COx,
0 etc
As
many
of
these by-products are toxic,
it
is
a
minimum
requirement
that
these gases are exhausted in an
enclosed
extraction
system
to
the
roof
of
the
building
-
following
health
and safety regulations. In
addition
to
this,
depending
on
local regulations,
it
may be necessary
to
have some
form
of
gas scrubbing
before
releasing these materials
to
the
atmosphere.
Even
if
we
were
not
running
gases
through
the
system,
we
would
recommend
that
the
system exhaust
is
extracted correctly, since
the
pump
exhaust
will
contain small
droplets
of
pump
oil
which
are in
themselves
harmful
to
lung
function.
Another
important
consideration
is
the
gas absorbed in
the
pump
oil. Since
the
exhaust gases contain
HF
there
will
be a
build
up
of
HF
in
the
pump
oil. Therefore,
it
is
important
to
use
the
correct
protective
equipment
when
servicing
the
pump
or
changing
pump
oil, i.e. suitable gloves, protective
clothing,
filtered
facemask
or
breathing
apparatus.
It
is
also
worth
remembering
that
when
using O
2
processes
the
pump
oil should be Fomblin
oil
and NOT
mineral
oil
to
avoid risk
of
fire
or
explosive reaction
between
O
2
and mineral oil.
Process
Information
(Information
contained
in
this
document
is
confidential)
Printed: 08 January 2006 09:37 Page
17
of
30
Issue
1:
December 03
Plasma
lab
Oxford
Instruments
Plasma
Technology
System
Manual
3.3
3.3.1
PECVD
processes
PECVD
operating
parameter
ranges
For a
PECVD
tool
the
typical process
operating
ranges are:
Total
gas
flows
=150
to
3000sccm. The
maximum
depends on
the
type
of
pumps i.e.
their
maximum
flow
capacity,
their
pumping
performance, and
the
required
operating
pressure.
If
you
need
to
use a
low
pressure,
you
may have
to
limit
flow
rate
to
achieve this.
Pressure =200
to
2000mTorr.
Below
300mTorr
the
plasma may
not
strike easily (or
with
sufficient
stability)
for
certain gases and
power
levels,
so
you
need
to
check this and adjust process accordingly,
since
operating
the
system
without
a plasma could cause damage. This
is
because
it
is
likely
to
cause a
high
reflected power,
or
dumping
of
power
into
matching
unit.
It
is
always essential
to
check
for
a
plasma. You can use
the
low
pressure strike
feature
in
the
software
to
allow
easier
striking
for
low
pressure processes. For certain flow/pressure combinations,
the
pressure
controller
may have
difficulty
in
maintaining
a constant pressure,
therefore
this may also be a
determining
factor
in
the
flow/pressure
used.
RF
power
=typically 20W
to
300W. A plasma may
not
strike easily
for
low
power
levels
for
certain
gases.
You
will
need
to
check this and adjust process accordingly, since
operating
system
without
a plasma could
cause damage.
Temperature
=
room
temperature
to
400C
(or
up
to
700C
for
a 700C stainless steel electrode). Film
quality/density
will
be worse
at
lower
temperatures,
therefore,
it
is
recommended
to
operate
at
the
maximum
temperature
that
the
substrate
will
allow
for
best
film
properties.
The system base pressure
for
PECVD
chambers
is
often
measured simply by using
the
CM gauge, hence
base pressures are typically a
few
mTorr. The exact value
is
mainly
determined
by
the
offset
of
the
CM
gauge
zero (this
is
usually set
slightly
positive
by
a
few
mTorr
to
ensure a sensible reading, since a
negative
offset
will
always read zero).
Operating
with
a
high
reflected
power
(>5%
of
forward
power)
is
not
advised
as
this
will
cause damage
to
matching
unit
or
generator. In such
cases
it
will
be necessary
to
adjust process parameters
or
re-tune
the
matching
unit.
3.3.2
Low
frequency
matching
The
uniformity
of
nitride
films
is
usually worse
for
Low
Frequency
(LF)
deposition
since
the
LF
is
closer
to
DC
and hence
is
much
more
sensitive
to
the
electrical conductance
from
electrode
to
plasma, and
from
plasma
through
wafer
and back
to
ground.
So
if
the
chamber
and/or
table
are
dirty
then
there
is
likely
to
be
more
non-uniformity
in
the
LF
film.
It
is
recommended
that
when
performing
an
LF
or
mixed frequency deposition,
that
the
customer should
do
a
brief
conditioning
of
a
few
thousand angstroms, and
then
endeavor
to
keep
that
constant thickness
of
film
on
the
table
under
the
wafer
throughout
the
subsequent runs. This means
putting
dummy
wafers
or
Aluminum
blanks over
the
unused
wafer
position
to
avoid a
build
up
of
film
in
the
unused locations,
because
it
is
known
that
these locations
will
give a very
poor
uniformity
if
this procedure
is
not
carried
out.
If
this does
not
cure
the
problem
then
it
may
be
that
the
system needs a
thorough
clean, back
to
bare
Aluminum.
Initially, using a plasma clean,
but
if
that
doesn't
work,
a bead-blast
of
the
showerhead
or
the
table
may be required.
It
is
not
recommended
to
use an
IPA
or
water
wipe-down
of
the
chamber
interior,
-just
an occasional
dry
wipe-down,
if
necessary,
to
remove loose
powder.
This should
only
be
done
with
the
system stone cold
(to
avoid meltinglresidues
of
clean
room
wipes
on
hot
surfaces).
Process
Information
(Information
contained
in
this
document
is
confidential)
Issue
1:
December 03 Page 18
of
30 Printed: 08 January 2006 09:37