Thanks for all your suggestions. Finally, what worked is a Fluorine
based dry etch with CF4+O2. Pure O2 plasma and even hot Piranha were too
slow. I had to sacrifice some oxide but the timing was short enough so the
oxide loss was within acceptable levels.

-Ameya



On Thu, Jun 24, 2010 at 12:11 PM, Michael D Martin <
michael.martin@louisville.edu> wrote:

> I agree with Mike.  Try using a RIE or DRIE oxygen plasma, its easy and
> safe.  In a March 1701 RIE we would run 300-400mT of O2 at 300-400W.  Though
> I would add that you might want to try a CF4 ~16-20% + O2 step for say 30
> seconds for a little more aggressive removal of material in addition to the
> oxygen etch.