There are two other possibilities that I see. First of all you could try
heating up the sample close to the glass transition temperture. We've
done that and it seems to work. The sample would perform sort of a
reflow then.

The other possibility would be using a negative resist where you can
perform grayscale lithography to get a round profile into your resist
that is then transfered into your silicon by etching.

All the best,
Marcel


Jaibir sharma schrieb:
> Dear Chen,
>
>                You can try dry thermal oxidation and then etching the oxide
with the help of BHF.
> I am not very sure with this but feel it may solve your problem.
>
> with regards
> jaibir
>

Marcel Spurny, Dipl. Phys. MPhys.
School of Physics & Astronomy
University of St. Andrews
North Haugh
St. Andrews
KY16 9SS
Fife
Scotland, United Kingdom
Tel.: 01334 467336