Pradeep,

Two suggestions,
1. You may need a high RF power, say, more than 1kW.
2. Why AZ9260? By my feeling, think photoresist can not get very vertical
wall, so the wall can not be kept vertical during the transferring. I would
recommend SiO2 as a mask which also has higher selectivity to Si.
3. High (I can figure how high, need to be optimized) chamber pressure is
helpful for increasing the selectivity.

Good luck,

Hongjun Zeng, PhD
Microfabrication Application Laboratory (MAL)
University of Illinois at Chicago

-----Original Message-----
From: Pradeep Dixit
Subject: [mems-talk] Through Hole etching of evry deep holes - Aspect ratio-
25-30

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.