Saphire will VERY slowly dissolve in concentrated HF and that is it.  Ion
bombardment is likely the way to go but the resist will go first. You could
deposit SiO2 thru a mask by pvd or pecvd and then heat the substrate to
react the SiO2 and Al2O3 into what is essentially a refractory glass and
that will etch faster in HF.  Just some thoughts, Gary

Gary Hillman
S-Cubed
PO Box 365
9 Mars Ct.
Montville, NJ 07045
phone 973-263-0640 ex 35
fax 973-263-8888
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-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of
Kirt Williams
Sent: Tuesday, June 14, 2011 7:48 PM
To: 'General MEMS discussion'
Subject: Re: [mems-talk] Etching 200 nm into a Saphirre Wafer


I tried a number of wet etchants on sapphire and found nothing that really
worked because sapphire is so inert. Some kind of sputtering like ion
milling with argon will etch anything because it's a physical removal
process.

   --Kirt Williams