How wide are the structures you like to release and what concentration
HF do you use? Etch rates vary from approx 0.7nm/min for 2per cent HF to
about 20nm/sec for 48 per cent. We use 5 per cent HF giving approx
50nm/min, this gives a very smooth Si bulk surface.

Karin

adongszju@hotmail.com schrieb:

> Dear colleges,
> I use 80um thick device layer SOI wafer to fabricate a MEMS structure
> with DRIE. The box layer is 1.2um thick.The trenches in the structure
> is 80um deep and 5um wide.When I release the structure with HF
> solution, I find it can't be released after many hours!what is the
> problem? The depth/width ratio is too high?
> Thanks for your possible help!
> Weidong Shen
> Zhejiang University,Hangzhou,P.R.China


--
Dipl.-Ing. Karin Buchholz
Walter Schottky Institut
Technische Universitaet Muenchen