stsetch systematic problems

Huang Kevin kevhuang at
Mon Nov 28 12:15:39 PST 2005

      I've been doing etching on SOI for 2 um wide pillars 10~30 um deep.
And I also noticed footing problem and more importantly, micrograssing is
getting more and more frequent for these past few months.


On 11/28/05, Matt Hopcroft <hopcroft at> wrote:
> Hello,
>        We've noticed increasing problems with the sts, and I'd like to
> put some information out and get some feedback from other people who may
> have been experiencing similar problems.
>        We've are etching 1 - 2 um wide trenches in SOI wafers with a 20
> um device layer and stopping on the buried oxide. We have been doing
> essentially the same type of etch since 2000. In the Fall of 2004, about
> 12 months ago, we started having problems with the etch: footing,
> mousebites, and incomplete etching. These results are illustrated in the
> attached pdf. The problems are intermittent- results vary from day to day,
> wafer to wafer, and across wafers, and over the last 12 months they have
> become more frequent. We have tried all kinds of combinations of resists,
> development cycles, pre-bake, post-bake, etc etc. Oxide hardmasks do seem
> to reduce the mousebite problems; but why? And why now?
>        Is anybody else seeing these problems? Has anyone else noticed a
> similar increase in problems in the past 12 months? Any thoughts are
> appreciated. Thanks,
> -Matt Hopcroft
> hopcroft at
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