Hello,

I am writing for advice regarding the adhesion of gold films to PMMA
films.

The situation is as follows: we have a silicon wafer onto which we
spin coat a thin film of PMMA (molecular weight =495,000) with nanometer
smoothness.  Good adhesion (actually great) between native
oxide on silicon wafer and PMMA film.  Subsequently we evaporate gold w/o
any chrome or titanium as an adhesion promoter.  Chrome or titanium
would probably ruin my device as my wet etch doesn't like these metals.
Also while they are great adhesion promoters on silicon wafers, it's not
clear that they would help at all on a PMMA film.  Anyways, the gold
film is very smooth initially though it rubs off easily if one drags a
finger across the film surface.  We want to do some gold patterning a la
Whitesides. The problem is that while the gold film initially looks
pretty, it delaminates partially during the subsequent wet etching step
involving KOH and ferrous cyanides. We're wondering if there is a standard
trick to increase the adhesion of the gold film to the PMMA via for
example, putting down a long alkane chain with a thiol terminus between
the gold and the PMMA.  All my literature searches/web searches have not
come up with any obvious solutions to this problem.  Any light you could
shine on this problem would be much appreciated.

Regards,

Christopher