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" 
To: ; "'General MEMS discussion'"

Sent: Friday, April 04, 2003 11:15 AM
Subject: RE: [mems-talk] C4F8 etchant


> 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: anupama@ee.washington.edu [mailto:anupama@ee.washington.edu]
> Sent: Thursday, April 03, 2003 8:14 PM
> To: mems-talk@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: (206)-221-5340
> email: anupama@ee.washington.edu
>
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