Letting the wafer sit for so long is obviously not a good idea.

Try something called ACT970.

You can also try hot NMP (~90C).  (use extreme caution)

The LOR is TMAH/KOH soluble.

You can also try heating the wafer to 150C.  This may reflow the resist
and break the ZrO2, which will help.

Delicate Mechanical cleaning or Megasonic/Ultrasonic agitation will also
help.

You can also do blanket expose (massive dose) to break down the photoresist.





Xiaoyuan Lou wrote:
> Hi, all
>
> I have a sample with photoresist on which is put aside for quite a long time
> (say half a year). The photoresist is "lift-off photoresist LOR-10B" and
> "positive photoresist S1813".
>
> After I sputtered ZrO2 on it, I can not lift them off by acetone or develop.
It
> looks like too strong. Does anyone here know why? Does long time storage cause
> any problem?
>
> How can I dissolve this? should I use stronger solvent?
>