rookie questions

Jim McVittie mcvittie at snf.stanford.edu
Thu May 6 13:48:11 PDT 2004


Ignacio,

Switching from a resist mask to a oxide mask would likely affect the etch
process. Plasma etch processes are tuned to particular wafer and chamber wall
surfaces. Changing a surface material usually affects the spieces mix in the
gas phase about the wafer and thus affects the etch results. If you want to
put the time into it, you can probably develop a process to work with a oxide
mask. I would look at some of the papers published on the Bosch process to see
if someone has already done the work to tune the process for an oxide mask. I
can cantact STS and see what they recommand. As is, the present process may
give acceptable results for your needs. I expect
users have oxide mask results.

Regarding the P-5000, etching the oxide and then etching the Al should work.
The advantage of
using the P-5000 ox etch over the AMTetcher is that the P-5000 is near 10X
fast (single wafer) and the end point detect is functioning. In addition, it
gives a steeper profile. The downside is that the selective to Si is worst.
Note that AMTetcher actually has two endpoint detectors (laser and optical
emission). The last time, I checked niether one was setup properly. If needed,
I can set them up.
                Jim McVittie

"Ignacio A. Zuleta" wrote:

> Dear STS users,
>
> I am in the process of optimizing a process flow that involves the use of
> the STS machine here in the lab. I am considering using oxide as a mask,
> and I wanted to check that I am thinking about the process right. I am
> planning to use tylanbpsg to put oxide on a Al-coated double-polished
> wafer(just one side), then I planned to pattern the oxide (and the Al
> layer) with the same mask using the P5000, finally STSetching trenches and
> release windows on the front and back of my wafer, respectively. The
> questions I have are:
>
> * Is the P5000 plasma etcher the right tool to pattern the oxide?
>
> * Are oxide masks better in any sense than PR masks in an STS etch?
>
> Thanks,
>
> Ignacio
> --
> Ignacio A. Zuleta
> Chemistry Department
> Stanford University
> Office: (650)723-4332
> Cellphone: (650)799-9225
> Fax: (650)725-0259
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