Maybe you can try to add your ratio for HF,At the same time you can obtain a
highly etching rate.
----- Original Message -----
From: "Isaac Wing Tak Chan" 
To: "General MEMS discussion" 
Sent: Tuesday, July 15, 2003 4:36 AM
Subject: Re: [mems-talk] Wet and Dry Etching.


> Hi Sungjin,
>
> For wet etching, using a higher hardbake temperature will usually
> improve the linewidth control and photoresist adhesion to the underlayer,
> assuming HMDS has already been used to promote adhesion. But you may need
> to use O2 plasma to strip the resist afterwards because it is highly
> crosslinked.
>
> For dry etching, CF4 + O2 plasma may erode your resist more
> quickly because O2 is used to ash resist. CHF3 will improve selectivity
> and anisotropy for sure. SF6 is a fast and isotropic etchant, at least at
> room temp. etching. But you may try Ar + SF6 or Ar + CF4 with high Ar
> ratio, besides CHF3. Good luck on your process.
>
>
> Yours sincerely,
>
> Isaac Chan
>
> Ph.D. Candidate
> Dept. Electrical & Computer Engineering
> University of Waterloo
> 200 University Ave. W
> Waterloo, Ontario, Canada
> N2L 3G1
> Tel: (519) 729-6409, ext. 6014
> Fax: (519) 746-6321
> [email protected]
> http://www.ece.uwaterloo.ca/~a-sidic
>
>
>
> On Tue, 15 Jul 2003, Sungjun Lee wrote:
>
> > Dear all:
> >
> > MEMS is not my major but I need to do a simple process.
> > Recently, I have worked SiO2 etching using a PMMA etch mask(100nm
thickness).
> > My goal is to etch SiO2 about 400A depth.(There should be PMMA alive for
the lift-off process)
> > About 300nm is the width of lines written by e-beam lithography.
> >
> > In wet etching with 25:1 HF, I failed to get some good results.
> > (PMMA was peeled off at around 120 seconds, and the etch depth is less
than 100A during this time)
> > Does anyone who use my condition in wet etching?
> >
> > We have a Oxford Etcher(plasmalab 80+).
> > The 100nm-PMMA is nearly wiped-out in my conditions:
> > CF4(40sccm) + O2(5sccm) under 50mtorr, 50W for 90 seconds.
> > Now, I can use some other gases, Ar, SF6, and CHF3.
> > Is there someone who try to other conditions?
> >
> > Could you please give your invaluable comments to me?
> >
> > Thanks in advance.
> >
> > Sungjun / Graduate Student.
> >
> >
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