[mems-talk] Lift-off process

[Jesse D Fowler]

HI Jeffrey,

I have used 5:1 Piranha to clean this sort of thing in the past. Chrome 
and gold are both pretty tough. If you had used Ti for adhesion, it would 
not work, but you should be all right for a minute or two. Oxygen plasma 
(followed by an acetone rinse/soak) may work well, as your PR is so much 
thicker than the metal.

In terms of what went wrong, it sounds like the PR got hard baked. You can 
try to reduce the thickness of metal, the deposition rate, or deposit it 
in stages with a rest between depositions.

Also, you can reduce the debris from sonication by removing the wafer 
while the sonicator is still on.

Jesse Fowler


"Yue Mun Pun, Jeffrey" <g0500396 at nus.edu.sg> 

Hi,
I am attempting a lift-off technique to pattern gold.  I have patterned 
7-8um of AZ9260 on SiO2 wafers and evaporated 10nm Chromium followed by 
300nm Gold through the patterns in the AZ9260 resist.  Subsequently I have 
lifted off most of the resist by soaking the wafers in Acetone over 2 
days.  However I have noticed that there are some resist residue that 
won't be lift-off even after sonication.  The sonication process also 
leaves a lot of debris on the wafer.
I am trying to remove these debris and the remaining residue by soaking 
the wafers overnight in AZ300T Stripper.  Does anyone have an alternative 
technique to suggest to clean the wafers?  I have tried using H2SO4:H2O2 = 
3:1 (piranha) by it may damage by structures, so I refrain from using this 
technique.