Piranah might attack CR. Also, in some ashers, the lines can heat up and
disappear. I would try Fuming HNO3 - it's a nasty acid but very effective at
cleaning chrome masks.

Shay

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Joseph
Grogan
Sent: Friday, March 26, 2010 6:38 PM
To: [email protected]
Subject: Re: [mems-talk] Cleaning optical masks

I second the Piranha safety warning. But also, according to "Etch Rates
for Micromachining Processing - Part II" Piranha eats evaporated Cr at
over 16 nm/min. I've used Piranha to clean masks before, but only as a
last resort and for short times. I would start with the oxygen asher and
exhaust that option before trying the Piranha. If the power was high
enough I can imagine that there's a small chance you could sputter off
Cr, but the rate would be immeasurably slow and I think you'd be risking
more harm to the mask with Piranha.

-Joe