Dear colleagues:

I would like to get suggestions on fabrication processes.  I am designing a
process for fabricating a device containing three levels of etched features
on a silicon wafer.  The features include basins of about 10 micron deep,
trenches of about 50 micron wide and 50 micron deep, and narrow
through-holes (etched all-the-way through the silicon wafers of 300 to 450
micron thick).  I am considering the use of Si(110) substrates and KOH wet
etching for achieving the arrow through-holes.  It seems that I have to go
through at least three etching steps in order to achieve three levels of
depth.  My difficulty is at the photoresist coating between the steps.  Any
one of my device features would cause sufficient corrugations on the
substrate surface and make uniform photoresist coating impossible.  I would
like to hear any suggestions on the overall process design, suitable etching
processes (wet or dry), and any tricks and/or materials that may make the
fabrication easier.

Thank you very much.



Xiaochuan Zhou, Ph.D.
Xeotron Corporation
E-mail xczhou@xeotron.com