Previous attempts using normal fabrication techniques (cleaning, resist spinning, baking, photolithography, resist development, plasma asher, metallisation - gold/titanium and ethanol liftoff) led to gold electrodes with poor adhesion. The gold was easily scratched off. Are there any addition fabrication steps required, or a different metal to titanium to promote adhesion.
I had earlier tried gold IDTS on alumina substrates using thermal evaporation. a thin layer of nickel before gold coating was useful for better adhesion.
Titanium is normally a very good adhesion layer for gold. If the Ti does not adhere well this could have 2 reasons:
1. The Ti is already oxidized during sputtering. You have high base pressure, a leak in your deposition system of contaminated Ar gas. Also, make sure you condition the Ti target by first doing a dummy run to clean the target.
2. De PI film surface is not wel prepared. This can contain H2O or OH-groups which migh prevent good adhesion. Try using a sputter etch on the PI substrate just before you start depositing the Ti.
Deposition of metals on flexible substrates and the patterning of the same are tricky affairs always. Adhesive layers like Ti or Cr might help sometimes. Usually adhesive layers (Ti or Cr) are used in Si substrates to manage the lattice mismatch between Si and Au.
In this case, I would suggest you to go for patterning the metal by etching on polyimide film instead of working with lift-off. You can use mild etchants to etch Au and Ti without affecting the polyimide film. Lift-off always gave me some problems, but etching always worked well..!
If laminating is at all relevant to you, perhaps look at US5306741 an old IBM patent. Sounds (and probably is) complicated
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