Sharukh, you can take O2 out and use pure CF4. If your mask still can't
withstand it, you can add about 10-20% H2 to CF4. You can also use CHF3
instead. Also, low rf power to reduce mask erosion. Since you are only
etching 50nm Si, etch rate is not much of a concern.

Regards,
Isaac Chan, Ph.D.


On Wed, 20 Sep 2006, l ll wrote:

> I would like to know if you knew about any dry etching techniques which would
help me etch single crystal Silicon (approximately 55 nm) using a thinned out AZ
resist as a mask. We have been experimenting with different gasses and their
combinations in a micro RIE. CF4 and O2 can not be used since the both attack
the AZ resist. We have no provisions in the clean room to use HBr or Chlorine.