Etching low stress SiN in MRC

Jim McVittie mcvittie at snf.stanford.edu
Mon Jul 26 14:30:10 PDT 2004


Venkatesh,

In looking at my notes for the AMT etch processes, I can say the following for the
MRC etcher. In etching Nitride with CHF3/O2, the nitride etch rate should increase
near linearly with O2 flow until the O2 flow gets to about 50% of the CHF3 flow. The
oxide etch rate will also increase with O2 flow but at a slower rate. Thus the
selectivity of  nitride to oxide etching increases with O2 flow. The selectivity to
Si and PR will decrese with O2 flow.  In the AMT etcher, nitride etch rate increases
with total flow up to a flow of 200 sccm. I do not know the flow at which the etch
rate peaks in the MRC but it will be much less than then 200 sccm valve for the
AMT.  The nitride etch rate should increase a bit less than linear with rf power,
however resist burning tends to be a problem at higher rf power levels.

Hope this is useful.
    Jim

Venkatesh Hanumant Rao Chembrolu wrote:

> Hi,
>
> I am trying to etch 300nm of low stress silicon nitride in MRC (this is for a 5"
> wafer which doesnot fit into Drytek 1) with 1.6um photoresist as the etch mask.
> I am thinking of using the nitride etch recipe for MRC (Oxygen 3sccm, CHF3,
> 15sccm, 50mT, 50W) and would like to know if someone has done anything similar
> before. Thanks.
>
> Venkatesh
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