Hi,

I have tried amost everything under the sun to avoid delamination of SU-8
from SiO2 substrates in KOH. These have included adhesion promoters to
improve interface bonding conditions and SU-8 processing modifications to
reduce interface delamination due to differential thermal
expansion/retraction. To cut a long story short - nothing worked. In all
cases, the SU-8 structures generally peeled from the substrate after seconds
or minutes in KOH. Chemical bonds at the SU-8/SiO2 interface simply cannot
withstand aggressive aqueous solutions and they quickly degrade and
fail soon after exposure. I only managed to overcome the adhesion
problem by generating physical restraint at the interface. By forming pits
with overhanging sidewall profile in the substrate using RIE, then applying
SU-8 and curing as normal, one can achieve robust mechanical interlocking.
This is sufficient to retain SU-8 structures to SiO2 substrates immersed
in aggressive media; inluding KOH.

http://ej.iop.org/links/q07/6VcFhqMS52v66PL294DI6A/jmm5_11_012.pdf

Good luck!

michael



> >Hi all,
> >
> >I am wondering if someone can advise me on how to improve the adhesion
> >between su-8 and oxide wafers.
> >
> >The su-8 film (20um thick) breaks and peels off from the wafer after KOH
> >etch.
> >
> >I did hardbake the su-8 at 150C for 3 minutes after developing.
>
>