Use 20 nm Cr or Ti as adhesion layer before the Ni deposition. Ni's stress
makes it easier to flake off especially if the thickness is big.

Another thing, since it sounds your etching is not significantly deep; you
can directely use Al as mask. If you do not like other metals mask, SiO2 is
a good option.

Good luck,

Hongjun Zeng, PhD
MEMS/Nano Scientist
Nanotechnology Core Facility
(NCF formerly MAL)
University of Illinois at Chicago
3064 ERF Building
842 W. Taylor St., Chicago, IL 60607
Tel. 312-355-1259, Fax: 312-413-0447

-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Yiyi Zeng
Sent: Tuesday, April 17, 2007 10:52 PM
To: [email protected]
Subject: [mems-talk] Ni lift-off problem

Dear all,

I'm working on deep dry etch of p-Si (>10um) and I was trying to evaporate
Ni as etch mask. I was trying to use lift-off technique and my photoresist
was AZP4110. The problem is when I was washing away the photoresist using
Acetone, almost all of the Ni, no matter on the photoresist or on the Si,
fell off the wafer. I tried three times and the results were same, but when
I previously evaporate Al and Cr, I didn't see this kind of problem. I'm
wondering if anyone has the similar experience? Did I do anything wrong? Any
suggestion to improve the process?