Dear Patrick,

I do not have any experience with such etching processes, but it sounds to
me that your quartz wafers have a sub surface damaging problem. If glass or
silica is ground and polished small cracks which exist after grinding will
be closed during the polishing by a mixture of the abrasive material, water
and quartz. This leads to smooth surface, but only covers this damaging.

Plan Optik GmbH in Germany has developped a polishing method called MDF
polishing (micro damaging free) which leads to surfaces without this
negative effect.

For further information please feel free to contact me.

Best regards,

Carsten Wesselkamp

Plan Optik GmbH
Unter den Eichen
56479 Elsoff
Germany
Tel.: +49-2664-5068-25
Fax: +49-2664-5068-91
http://www.planoptik.com




Message: 3
Date: Mon, 5 Apr 2004 12:15:15 -0700
From: "Patrick Lu" 
Subject: RE: [mems-talk] CORRECTION: fabricating optics with reflowed
        photoresist in plasmaetcher, problem with surface roughness
To: "'General MEMS discussion'" 
Message-ID: <[email protected]>
Content-Type: text/plain;       charset="us-ascii"

Sorry, I meant CF4 not CH4. :)

Patrick Lu
Stanford University
Department of Electrical Engineering
http://www.stanford.edu/~patlu

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
Patrick Lu
Sent: Sunday, April 04, 2004 12:39 AM
To: [email protected]
Subject: [mems-talk] fabricating optics with reflowed photoresist in
plasmaetcher, problem with surface roughness

Hi,



I have quartz wafers covered with reflowed photoresist. I am etching these
with a mixed CH4 and O2 plasma. Hopefully, I will be able to adjust the
height of the resulting optic by changing the gas concentrations (with CH4
etching the glass and O2 etching the photoresist). Right now, the optics
that come out of the plasma etcher are very rough-much rougher than the
photoresist profiles that shaped them. Under a microscope, I see many cracks
in the surface of the quartz. The "bumpiness" is on the order of 1/3 of a
micron (where the optic height is 1 - 2 microns). I am running at a pressure
of 150 mTorr, with gas flow rates of 100 cc/m for CH4 and 50 cc/m for O2,
and 83 W of RF power. If anyone has experience etching glass with reflowed
photoresist, their advice would be much appreciated!



Thanks!



Patrick Lu

Stanford University

Department of Electrical Engineering

http://www.stanford.edu/~patlu