If it is photoresist redeposition, try operating at a lower power (using an
optimized process) and use Helium-backside-cooling if you have it as an
option.  In my experience with high plasma density systems, the
Helium-backside-cooling makes a huge difference in terms of preventing
burning of the resist.  It may help the redeposition problem as well.

For RIE of SiNx films, look for papers from Gottleib Orlein.  I forget where
he is now; he used to be at SUNY Albany.  This may guide you in finding a
lower power process.
-Bill

On Mon, 25 Oct 2004, Z.,W.Y.(Lydia) wrote:

> Dear all,
>
> When I preformed a plasma etching, i,e.,using CF4 etched Silicon Nitride
> (100nm) on top of silicon and the photo resist (OCG825) as a masking
layer, I
> had a problem that the PR re-deposited to the opened (silicon) area. Under
> microscope, the opened (silicon) areas looked like light red. How can I
get
> rid of this problem? Any advise are appreciated! BTW, my etcher is
Technics
> West Inc., PE II-A Plasma System.
>
> Have a nice day!
>
> Lydia
>