Tony:

You will want to avoid oxygen since any oxygen will slow the BST etch rate
and also increase PR loss.   Your best bet is probably the CF4.  The SF6 is
likely to have lower selectivity to the mask than the CF4 and the
consumption of fluorine is likely to be low so the difference in BST etch
rate is likely to be small.  The hydrogen could help.

Robert

On Mar 25, 2011 2:45 PM, "Tony Price"  wrote:
> I plan on using S-1813 positive resist as a mask. The gases that I have
> available are SF6, CF4, O2, and H2. Which one of these would you
recommend,
> if any?
>
> Thanks,
> Tony