When you tried Al and Cr, they worked because they had good adhesion to the
Si.
Ni does not have good adhesion to Si (really to the native oxide layer on
Si).
Start with ~100 A of Cr or Ti as an adhesion layer, then deposit your Ni. Do
this without breaking vacuum.
    --Kirt Williams

----- Original Message -----
From: "Yiyi Zeng" 
To: 
Sent: Tuesday, April 17, 2007 8:52 PM
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?