H2SO4:HP3O4 should etch sapphire at lower temps than 300 but the etch rate
will be very slow. Etch rates for micromachining table shows 160°C 1:1 mix
will etch at 0.3 nm/min.

Mark West

-----Original Message-----
From: Gary Hillman [mailto:garyh@s-cubed.com]
Sent: Wednesday, June 15, 2011 12:23 PM
To: kirt_williams@sbcglobal.net; 'General MEMS discussion'
Subject: Re: [mems-talk] Etching 200 nm into a Saphirre Wafer

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
Check out our web site and Twitter at www.s-cubed.com


-----Original Message-----
From: mems-talk-bounces+garyh=s-cubed.com@memsnet.org
[mailto:mems-talk-bounces+garyh=s-cubed.com@memsnet.org]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