If you have respectible etch control, you could do four etches of 2um, 1um,
0.5 um, and 0.25 um.  With four masking layers you could achieve 16 depth
levels.  Then a smoothing anistropic etch to even the thing out.  I'm not
sure how the alignment issues would work out, but I'd imagine you'd want to
err on the side of bumps (not pits) on the transition points.

Actually, and anisotropic etch might be better at smoothing things out, as
it attacks corners rather aggressively.  You'd have to try it to see.



David Nemeth
Senior Engineer
Sophia Wireless, Inc.
14225-C Sullyfield Circle
Chantilly, VA 20151

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of [email protected]
Sent: Wednesday, April 19, 2006 9:45 PM
To: [email protected]
Subject: [mems-talk] Silicon Ramp Needed


OK Mems people, work with me. This is a real question.  How can I make a
silicon ramp 5um tall on one end and 1um on the other, 250um long, 5um
wide?  I'm starting with a 5um layer of Si on a substrate.  The real
question is how to etch/make a smooth, ramp, type structure.  I feel a few
lith steps of 1um 4 times to build "stairs" and then figure a way to smooth
the 1um steps.  Anyone????