Actually, I just realized I'm confused - what material are you trying to etch?
I'd thoughtlessly assumed you were fabricating your PDMS master in Si, but HF is
an SiO2 etch with high selectivity versus Si.  If you want to etch SiO2
isotropically without HF / BOE, you could try "Pad etch" - a solution of NH4F
and acetic acid designed to etch SiO2 with high selectivity versus Al.  It's
slower than BOE, but doesn't involve HF.  However, if you wanted to do your
process in Si, you could use Si Iso wet etch (aka "trilogy etch") if you don't
have access to XeF2, and get very good anisotropic/rectilinear trenches using
DRIE.

Also, I'll point out that the oft-cited Kirt Williams etch rates paper is a good
quick reference if you're looking for ideas on "what etches what?"  There are
obviously more possible chemical systems out there, but that paper does a great
job of covering all the standards that you might expect in a standard research
cleanroom.

That said, BOE (buffered HF) really is the standard wet etchant for SiO2, and
it's worth knowing how to work with it if you're going to be doing this more
than once.  HF is certainly a hazardous chemical, but as long as the user has
appropriate training, good awareness, and proper safety equipment (strong acid-
oriented fume hood, HF-safe teflon labware, PPE, spill kit including calgonate)
it's very managable.  Of course, if your lab doesn't have proper safety
protocols and someone to train HF users, I'd be much more wary of simply picking
it up and using it.  But still, there are plenty of other commonly used
chemicals and mixtures in a fab that can lead to serious safety problems if used
improperly - piranha is notorious, for example.

Good luck,
Mike

_______________________________________________
Hosted by the MEMS and Nanotechnology Exchange, the country's leading
provider of MEMS and Nanotechnology design and fabrication services.
Visit us at http://www.mems-exchange.org

Want to advertise to this community?  See http://www.memsnet.org

To unsubscribe:
http://mail.mems-exchange.org/mailman/listinfo/mems-talk