C4F8 etchant

[a***@ee.washington.edu]

Hi MEMS Community,

I would like to know if anyone knows of a chemical that
would etch C4F8 (octofluorocyclobutane)

During the DRIE process, C4F8 is deposited for sidewall
passivation and mask protection in the alternate deposit and
etch cycles. After the DRIE I remove the photoresist AZ4620
by putting the wafers in a Barell Asher with O2 plasma
(40mTorr, 300 Watts for 10mins) and subsequent treatment
with resist strips EKC for 10 mins at 60C and AZ300T for 10
mins at 75C.
This I believe should remove the C4F8 deposits as well.

However from our SEM pictures we find that, possibly the
unremoved C4F8 acts as a mask for further Silicon etching
(in RIE)and this mask is undercut resulting in the loss of
our structures.

I would appreciate very much if someone on the list could
get back to be with an idea of how to strip the C4F8.

Sincerely
Anupama

Anupama V. Govindarajan
Graduate Student - EE MEMS laboratory
Department of Electrical Engineering
University of Washington
Campus Box 352500, Seattle WA 98195
Phone: [phone]
email: ***@ee.washington.edu

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[B***@aol.com]

Anupama:

Do you have the ability to add some CF4 to your plasma ash tool? Try using a 96:4 ratio of CF4:O2 at 100 watts for 5 minutes. You might have to experiment with time to get best results but if you are dealing with an inorganic residue of some sort it should take it off. Pressure around 250 mtorr. Bob Henderson

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[Burkhard Volland]

Hello.
-----Ursprüngliche Nachricht-----
Von: ***@ee.washington.edu <***@ee.washington.edu>
An: mems-***@memsnet.org <mems-***@memsnet.org>
Datum: Donnerstag, 3. April 2003 21:45
Betreff: [mems-talk] C4F8 etchant

Post by a***@ee.washington.edu
Hi MEMS Community,
I would like to know if anyone knows of a chemical that
would etch C4F8 (octofluorocyclobutane)

The polymers you are depositing are called "plasma polymerized fluorinated
monomer" (PPFM) films. The chemical formular depends on process conditions,
generally the films are more or less "teflon-like", consisting of
CF2-groups. Riccardo d'Agostino edited a book about the deposition and
etching of these films (Plasma deposition, treatment and etching of
polymers, Academic press, 1990, ISBN 0-12-200430-2), and also a number of
articles in "Journal of Vac. Sci. Technol.", "J. Applied Phys.", and "Plasma
Chem. and Plasma Process.". Find these articles on SPIN Web:
http://ojps.aip.org/spinweb/ -> search SPIN database. At least, you can
access the abstracts. Find articles with keywords "polymer" and "plasma" or
the like.

Post by a***@ee.washington.edu
During the DRIE process, C4F8 is deposited for sidewall
passivation and mask protection in the alternate deposit and
etch cycles. After the DRIE I remove the photoresist AZ4620
by putting the wafers in a Barell Asher with O2 plasma
(40mTorr, 300 Watts for 10mins) and subsequent treatment
with resist strips EKC for 10 mins at 60C and AZ300T for 10
mins at 75C.
This I believe should remove the C4F8 deposits as well.

Some researchers report difficulties in removing the polymer films in the
absence of energetic ion bombardement. If your device can survive ion
bombardment, you could etch the polymer in a RIE etcher, with high DC bias
(100 to 200V) oxygen plasma. Some researchers suggest a mixture of CF4 and
O2 as etching gases. Maybe a small addition of SF6 to your O2 will help to
remove the polymer. If you want to use wet etching, a solution called
"piranha" might do the trick, but I would prefer plasma etching. Does the
manufacturer of your DRIE etching tool suggest a cleaning recipe for the
chamber?


I use a mixture of CHF3 and Methan (CH4) as process gases for sidewall
passivation, and we have not yet found difficulties in removing the sidewall
passivation layer, by oxygen resist stripper (asher). We don't have an etch
tunnel, maybe that's why.

Regards

Burkhard

Post by a***@ee.washington.edu
Sincerely
Anupama
Anupama V. Govindarajan
Graduate Student - EE MEMS laboratory
Department of Electrical Engineering
University of Washington
Campus Box 352500, Seattle WA 98195
Phone: [phone]

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[Jason Viotty]

You could try a 'Piranha cleaning'. This mixture is know for its voracious
ability to remove organics, so it might help solve your problem. Typically,
mixtures of 98% H2SO4 (sulfuric acid) and 30% H2O2 (hydrogen peroxide) in
volume ratios of 2-4:1 are used at temperatures of 100?C and higher.

Regards,
Jason Viotty
___________________________________________________________
Jason Viotty
Senior Process Engineer
C2V
http://www.c2v.nl



-----Original Message-----
From: ***@ee.washington.edu [mailto:***@ee.washington.edu]
Sent: Thursday, April 03, 2003 8:14 PM
To: mems-***@memsnet.org
Subject: [mems-talk] C4F8 etchant


Hi MEMS Community,

I would like to know if anyone knows of a chemical that
would etch C4F8 (octofluorocyclobutane)

During the DRIE process, C4F8 is deposited for sidewall
passivation and mask protection in the alternate deposit and
etch cycles. After the DRIE I remove the photoresist AZ4620
by putting the wafers in a Barell Asher with O2 plasma
(40mTorr, 300 Watts for 10mins) and subsequent treatment
with resist strips EKC for 10 mins at 60C and AZ300T for 10
mins at 75C.
This I believe should remove the C4F8 deposits as well.

However from our SEM pictures we find that, possibly the
unremoved C4F8 acts as a mask for further Silicon etching
(in RIE)and this mask is undercut resulting in the loss of
our structures.

I would appreciate very much if someone on the list could
get back to be with an idea of how to strip the C4F8.

Sincerely
Anupama

Anupama V. Govindarajan
Graduate Student - EE MEMS laboratory
Department of Electrical Engineering
University of Washington
Campus Box 352500, Seattle WA 98195
Phone: [phone]
email: ***@ee.washington.edu

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MEMS-***@memsnet.org mailing list: to unsubscribe or change your list
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.memsnet.org/

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[Philip Lau]

Anupama,
If you have not already tried, use ACT-1, a hydroxyl amine based
solution which has been used in the past for cleaning chrome mask with
resist residue.

I suspect your sidewall polymer may have debri embedded in it.

Regards,

Philip Lau

----- Original Message -----
From: "Jason Viotty" <***@c2v.nl>
To: <***@ee.washington.edu>; "'General MEMS discussion'"
<mems-***@memsnet.org>
Sent: Friday, April 04, 2003 11:15 AM
Subject: RE: [mems-talk] C4F8 etchant

Post by Jason Viotty
You could try a 'Piranha cleaning'. This mixture is know for its voracious
ability to remove organics, so it might help solve your problem. Typically,
mixtures of 98% H2SO4 (sulfuric acid) and 30% H2O2 (hydrogen peroxide) in
volume ratios of 2-4:1 are used at temperatures of 100?C and higher.
Regards,
Jason Viotty
___________________________________________________________
Jason Viotty
Senior Process Engineer
C2V
http://www.c2v.nl
-----Original Message-----
Sent: Thursday, April 03, 2003 8:14 PM
Subject: [mems-talk] C4F8 etchant
Hi MEMS Community,
I would like to know if anyone knows of a chemical that
would etch C4F8 (octofluorocyclobutane)
During the DRIE process, C4F8 is deposited for sidewall
passivation and mask protection in the alternate deposit and
etch cycles. After the DRIE I remove the photoresist AZ4620
by putting the wafers in a Barell Asher with O2 plasma
(40mTorr, 300 Watts for 10mins) and subsequent treatment
with resist strips EKC for 10 mins at 60C and AZ300T for 10
mins at 75C.
This I believe should remove the C4F8 deposits as well.
However from our SEM pictures we find that, possibly the
unremoved C4F8 acts as a mask for further Silicon etching
(in RIE)and this mask is undercut resulting in the loss of
our structures.
I would appreciate very much if someone on the list could
get back to be with an idea of how to strip the C4F8.
Sincerely
Anupama
Anupama V. Govindarajan
Graduate Student - EE MEMS laboratory
Department of Electrical Engineering
University of Washington
Campus Box 352500, Seattle WA 98195
Phone: [phone]
_______________________________________________
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.memsnet.org/
_______________________________________________
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.memsnet.org/

_______________________________________________
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[Eric Sanjuan]

If your problem is coming from the C4F8 gas what your dealing with is
the removal of a fluorocarbon film, namely CFx where
x =1,2,3. Typical XPS data shows the F/C ratio of the fluorocarbon film goes
down with decreasing F/C ratio of the parent molecule. To put it short gases
like CF4 deposit very little in a HDP and C4F8 deposits a lot more i.e.
CF4<C2F6<C4F8<C6F6. If it is allowed ( I don't know why but peopIe recommend
against oxide etching and O2 plasma etching in DRIE tools, maybe someone
would be nice enough to explain is or put an end to the taboo ) I would use
the same source ( or another HDP source ) and do a O2 "Descum/PR strip" on
the wafers. These HDP sources are much more effective at etching polymers
than barrel or RIE etchers. The higher the source power the better, 10mT if
its some hard stuff ( check 10-~100mT ) and bias to the chuck will increase
the etch rate of the polymer also (you will get etching without bias). If
you have an OES system continue the O2 etch untill only the Oxygen (777nm
peak) is present. Hope this helps

eric

Message: 7
Date: Thu, 03 Apr 2003 10:13:55 -0800
Subject: [mems-talk] C4F8 etchant
Hi MEMS Community,
I would like to know if anyone knows of a chemical that
would etch C4F8 (octofluorocyclobutane)
During the DRIE process, C4F8 is deposited for sidewall
passivation and mask protection in the alternate deposit and
etch cycles. After the DRIE I remove the photoresist AZ4620
by putting the wafers in a Barell Asher with O2 plasma
(40mTorr, 300 Watts for 10mins) and subsequent treatment
with resist strips EKC for 10 mins at 60C and AZ300T for 10
mins at 75C.
This I believe should remove the C4F8 deposits as well.
However from our SEM pictures we find that, possibly the
unremoved C4F8 acts as a mask for further Silicon etching
(in RIE)and this mask is undercut resulting in the loss of
our structures.
I would appreciate very much if someone on the list could
get back to be with an idea of how to strip the C4F8.
Sincerely
Anupama
Anupama V. Govindarajan
Graduate Student - EE MEMS laboratory
Department of Electrical Engineering
University of Washington
Campus Box 352500, Seattle WA 98195
Phone: [phone]

_______________________________________________
MEMS-***@memsnet.org mailing list: to unsubscribe or change your list
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
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[Isaac Wing Tak Chan]

Hi Anupama,

Is your DRIE process for deep silicon trench structure? If yes,
what is the aspect ratio of the trench? Your O2 ashing process should be
able to remove the polymer deposit but it is aspect ratio dependent if the
ratio is high. Same for solvent stripper, if your opening size very small,
the surface tension of the solution may not allow it to reach the whole
trench. But if you are not doing this work, then something else like other
people suggested may be needed. Hope this helps.


Isaac Chan

Post by a***@ee.washington.edu
Hi MEMS Community,
I would like to know if anyone knows of a chemical that
would etch C4F8 (octofluorocyclobutane)
During the DRIE process, C4F8 is deposited for sidewall
passivation and mask protection in the alternate deposit and
etch cycles. After the DRIE I remove the photoresist AZ4620
by putting the wafers in a Barell Asher with O2 plasma
(40mTorr, 300 Watts for 10mins) and subsequent treatment
with resist strips EKC for 10 mins at 60C and AZ300T for 10
mins at 75C.
This I believe should remove the C4F8 deposits as well.
However from our SEM pictures we find that, possibly the
unremoved C4F8 acts as a mask for further Silicon etching
(in RIE)and this mask is undercut resulting in the loss of
our structures.
I would appreciate very much if someone on the list could
get back to be with an idea of how to strip the C4F8.
Sincerely
Anupama
Anupama V. Govindarajan
Graduate Student - EE MEMS laboratory
Department of Electrical Engineering
University of Washington
Campus Box 352500, Seattle WA 98195
Phone: [phone]
_______________________________________________
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.memsnet.org/

Yours sincerely,

Isaac Chan

Ph.D. Candidate
Dept. Electrical & Computer Engineering
University of Waterloo
200 University Ave. W
Waterloo, Ontario, Canada
N2L 3V1
Tel: [phone], ext. 6014
Fax: [phone]
***@venus.uwaterloo.ca
http://www.ece.uwaterloo.ca/~a-sidic


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[Michael D Martin]

I think manufacturers of DRIE's recommend against using O2 plasmas since
it attacks O-rings. In particular, on STS systems with He back side
cooling the O-ring that seals the back of the wafer gets degraded.
Despite this I have used short O2 etches in the STS system and it works
great! I have used these short etches not so much to remove the teflon
like polymer but to change its surface from one that is very hydrophobic
to hydrophilic so that it can be wet etched in Nanostrip.

good luck,
Mike Martin
If your problem is coming from the C4F8 gas what your dealing with
is
the removal of a fluorocarbon film, namely CFx where
x =1,2,3. Typical XPS data shows the F/C ratio of the fluorocarbon film
goes
down with decreasing F/C ratio of the parent molecule. To put it short
gases
like CF4 deposit very little in a HDP and C4F8 deposits a lot more
i.e.
CF4<C2F6<C4F8<C6F6. If it is allowed ( I don't know why but peopIe
recommend
against oxide etching and O2 plasma etching in DRIE tools, maybe
someone
would be nice enough to explain is or put an end to the taboo ) I would
use
the same source ( or another HDP source ) and do a O2 "Descum/PR
strip" on
the wafers. These HDP sources are much more effective at etching
polymers
than barrel or RIE etchers. The higher the source power the better,
10mT if
its some hard stuff ( check 10-~100mT ) and bias to the chuck will
increase
the etch rate of the polymer also (you will get etching without bias).
If
you have an OES system continue the O2 etch untill only the Oxygen
(777nm
peak) is present. Hope this helps

eric

Message: 7
Date: Thu, 03 Apr 2003 10:13:55 -0800
Subject: [mems-talk] C4F8 etchant
Hi MEMS Community,
I would like to know if anyone knows of a chemical that
would etch C4F8 (octofluorocyclobutane)
During the DRIE process, C4F8 is deposited for sidewall
passivation and mask protection in the alternate deposit and
etch cycles. After the DRIE I remove the photoresist AZ4620
by putting the wafers in a Barell Asher with O2 plasma
(40mTorr, 300 Watts for 10mins) and subsequent treatment
with resist strips EKC for 10 mins at 60C and AZ300T for 10
mins at 75C.
This I believe should remove the C4F8 deposits as well.
However from our SEM pictures we find that, possibly the
unremoved C4F8 acts as a mask for further Silicon etching
(in RIE)and this mask is undercut resulting in the loss of
our structures.
I would appreciate very much if someone on the list could
get back to be with an idea of how to strip the C4F8.
Sincerely
Anupama
Anupama V. Govindarajan
Graduate Student - EE MEMS laboratory
Department of Electrical Engineering
University of Washington
Campus Box 352500, Seattle WA 98195
Phone: [phone]

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