Hi!

I'm not sure, but i would try to increase power to get more anisotropic
etching result. I wouldn't use O2 at all, because it strips protective
polymer from side walls. In this way you will have more protective
coating at side walls and more ion bombardment to etch polymer away from
planar surfaces.

Temperature control is also used to enhance anisotropy. Cooling your wafer
during the RIE etching will suppres chemical etching. This is not possible
in all RIE systems.

********
Tommi

On Fri, 13 Feb 2004, frank berisford wrote:

> Hello all,
>
> Over the past few weeks I've been trying to get a highly anisotropic silicon
> dioxide etch recipe for 2 different feature sizes.  I was able to obtain
> acceptable results on 0.5 micron features.  However the recipe didn't work so
> well for larger (50 micron) features.  My current recipe is a CHF3/O2
chemistry
> at very low power and flow rates.  My optimised etch for the small features
has
> no effect on the larger features other than decreased etch rate.
>
> Thanks for any insight you can offer,
> Frank
>
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