debonding resist bonded wafers

Hello labmembers,

I am trying to debond two wafers which were resist-bonded using 7um thick SPR 220-7 resist. So far I have tried 1165 solvent at room temperature for over 48 hours, PRS-1000 at 40C for 2 hours, 1165 solvent heated to 80 C for 1 hour, as well as acetone at room temperature for 1 hour. However the wafers still haven't debonded. I cannot use piranha solution as this wafer has metal on it.

Could anyone suggest me what I should use to debond these wafers, and how long does it usually take.

Thanks,

Nikhil