The parallel-plate configuration gives some ion bombardment to the wafer,
which should result in a faster etch rate.

With a barrel configuration, many wafers are stacked parallel to etch other with
a small gap,
so the photoresist to be removed from each wafer is shielded by its neighbor.
The plasma is generated outside of the wafers. Oxygen radicals diffuse into the
space
between wafers and etch the photoresist. This does not have ion bombardment on
the wafers.

Also, because the oxygen-radical concentration is highest at the wafer edges,
the etch rate will be faster at the edges.
You might be able to improve uniformity by only etching one wafer at a time.

        --Kirt Williams Agilent Technologies


> -----Original Message-----
> From: Oray Orkun Cellek [mailto:cellek@metu.edu.tr]
> Sent: Friday, January 10, 2003 2:22 AM
> To: General MEMS discussion
> Subject: Re: [mems-talk] photoresist (Shipley series)
> thinning using low
> rate oxygen plasmaRIE
>
>
> Dear Mems-Talk Users,
>
> I have another question related to the plasma-etch thinning
> of Shipley PR.
>
> A Bio-Rad Barrel etcher, working at 150W 200mbar O2 plasma, etches
> photoresist much much slower than 35nm/min order (the value which
> Dr.Williams mentioned for parallel plate 50W) !
>
> No problem about PR bake, chamber-contamination and others ...
>
> Is such a slow etch rate a problem of barrel etchers or, is
> there another
> problem?
>
> Thank you for your help.
>
> Oray Orkun Cellek
> o.o.cellek@ieee.org
> Research Assistant, Ph. D. Student
> Electrical & Electronics Engineering Department
> Middle East Technical University
> 06531 Ankara
> Turkey
> Tel : +90 312 210 4579
> Fax : +90 312 210 1261
>
> ----- Original Message -----
> From: 
> To: ; 
> Sent: Thursday, January 09, 2003 7:40 PM
> Subject: RE: [mems-talk] photoresist (Shipley series)
> thinning using low
> rate oxygen plasmaRIE
>
>
> > > -----Original Message-----
> > > From: Wei Wei [mailto:wwei1@uci.edu]
> > > Sent: Wednesday, January 08, 2003 3:31 PM
> > > To: mems-talk@memsnet.org
> > > Subject: [mems-talk] photoresist (Shipley series)
> thinning using low
> > > rate oxygen plasmaRIE
> > > I try to use low oxygen plasma to thin my photoresist layer.
> > > If anybody
> > > have experience on this? Can you provide a receipe to control the
> > > etching rate under 100nm/min?
> > > Thanks,
> > > Alex
> >
> > Just reduce the plasma power to slow the etch rate.
> > As an example in a Technics PEII-A parallel-plate plasma etcher,
> > with oxygen at 300 mTorr,
> > at 400 W photoresist etches at about 350 nm/min;
> > at  50 W photoresist etches at about  35 nm/min.
> >
> > --Kirt Williams Agilent Technologies
> >
> > _______________________________________________
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http://mail.mems-exchange.org/mailman/listinfo/mems-talk
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