I am afraid silicon nitride will not work in my case. But it looks like the
SF6 worth a try. The SiO2 I am going to etch is around 100nm, not very deep
actually. I think the selectivity maybe OK.

I googled the web and saw some people use hot H2SO4/H2O2 to remove the
polymer residue.


----- Original Message -----
From: "Scott McWilliams" 
To: "General MEMS discussion" 
Sent: Wednesday, August 16, 2006 4:06 PM
Subject: Re: [mems-talk] How to remove the PMMA etching residue.


> Good luck Xiaojing, I saw someone else suggested adding SF6, I never tried
> that.  I have etched SiO2 with PMMA mask with 100% SF6 and it was
> consistently very clean, although you may have some selectivity
> requirements that require you to use a carbon-containing etchant.  I have
> always liked the idea of using SF6 etch and going with silicon nitride
> instead of SiO2. Is that an option for you?, the SF6 etches nitride really
> fast and clean.
>