Hi CHEN,
It's likely that the PMMA is already gone, and your sidewall was not
vertical enough. Have you considered negative e-beam resist?

Depending on the metals you deposited, you may be able to use something
far more aggressive. What metals were they?

Without knowing what the metal was, you can try various heated stripper
baths (like ALEG-355, PRS-1000, etc).

Jesse Fowler



Hongzhi CHEN  writes:
Hi,

I am using the e-beam to pattern my sample, the
resulotion is not very high, just around 500nm. It is
followed by depositing metal. After that, I use the
aceton to do the lift-off. My problem is that the
metal did not peel off as expected, after puting my
sample in the aceton for one day, no any metal peel
off. I need to use the ultrasonic to enhence the
lift-off process, after around 30 seconds ultrasonic,
most of the metal peel off. But some metal around the
pattern did not peel off even after around 10 miniutes
ultrasonic.

Is there any other chemical can remove PMMA better
than Aceton? Or is there any other way can enhance
this e-beam lift-off process? I appreciate any advice.