Hi Pradeep,

We have had success with through etches of small holes with high aspect ratios
using AZ4620.  The parameters will vary a lot from machine to machine so
there is no magic numbers I can give you.  You will most likely find that you
can only attain a good etch on one size of feature at a given set of
parameters and they will need to be adjusted for each change in feature size.
You might be able to find a compromise that gives you a "fair etch" on "most
features" depending on what you find acceptable.   My advice is to find out
what depth you can reach using your factory recipe and then decrease the
passivation time and/or passivation gas flow to reach deeper depths.  This
will cause undercut on larger features hence why I suggest you only try one
feature size at a time.

--
Shane McColman
Research Professional
NanoFab, University of Alberta

On April 25, 2005 08:20 pm, Pradeep Dixit wrote:

> I need to etch through holes of very fine diameter (15,20,25,30 and 35
> microns) in 450 um thick Silicon wafer. I am using 10 um thick AZ9260
> photoresist as mask.
>
> Standard bosch process is used. SF6- 130 sccm, C4F8-100 sccm, Platen
> power - 150 W. After etching a long time, i could not etch them
> completly. We have STS DRIE machine
>
> Anyone would like to help me in this matter. What will be the optimum
> parameters for though hole etching of very deep and narrow holes.