I need to find a sacrificial layer that could be spun between Silicon wafer and PDMS. Then I need to deposit gold on PDMS by thermal evaporation and Zinc Oxyde by sputtering. I already tried with photoresist but it was very hard to peel off my sample at the end without destroying everything due to the sputtering; I also tried water-soluble polymer as Polyvinyl alcohol but I need to sputter at high temperature (> 200 °C) and the polymer would evaporates..
Can anyone suggest idea to do a sacrificial layer that tolerate high temperature and doesn't require a solvent that would damage ZnO? Many thanks!
What about polyimde (applied by spin coating) and removal by oxygen plasma etching?
Thanks for your suggestion Alan!
I think I cannot use polyimide because plasma etching would destroy the layer of Zinc Oxyde and Gold that I have on top of the PDMS. I want to peel off my sample ( PMDS + Au + ZnO) from the substrate (Si wafer) without damaging anything.
Regards
Plasma etching in oxygen will only remove the organic material. It doesn't affect Au or ZnO....
Yes but the polyimide would be between the Silicon wafer and the PDMS, plasma etching would remove at the edges but how can I remove everything, even at the center. For information I'm using 4 inch (100mm) wafers.
Thank you for your help!
I think zinc oxide should be stable up to pH 13, and I think PDMS can also stand that (but I am not entirely sure), so maybe you could use a metal sacrificial layer that is not stable in alkaline conditions (aluminum?), and then soak your sample in 0.1 M NaOH/KOH for a long time to dissolve the metal layer.
Recently I used polystyrene, that you can be dissolves in toluene or acetone. I'm usually working around 150°C but it may still be ok at 200°C.
If you do not care about the thickness and and the surface quality of the layer "capton" tape in useful sometimes, but it's not appropriate for TEM measurements for example.
Good luck
Don't forge to share it if you find an interesting solution.
Hi Elie,
"Capton" (kapton) was mentioned above as polyimide - and it can be deposited from the solution actually, though the subsequent removal might be a problem.
I would support aluminium (0.1-1 um thick) as was also suggested.
It'll be a long base etching to remove tt from all the surface of 100 mm wafer, but this approach should work out. As a base you can use typical photoresist developer (2.38% TMAH, e.g. AZ726. AZ326 etc.)
I would use PVD deposited Molybdenum. This will withstand the normal temperatures during deposition and does not react with PDMS or Si. It can easily be remove with diluted hydrogen peroxide (which does not attack ZnO, I believe) and will lift-off easily. You only need very diluted peroxide and your liquid will turn blueish from the formation of the dissolvable molybdates.
- Badges
- Science topic