Electrode array fabrication on ITO coated PET foil

Lithography process

• Cut the piece of PET foil and stick it to a glass substrate. Careful, the ITO layer is quite breakable and easy to crack while bending. There are two ways of doing it. At first using a both side sticky tape, but then it is almost unpossible to detach the foil from the glass. The other way is to use parafilm instead of sticky tape, then apply some press and heat it to 50°C. The parafilm could be later removed

• Remove the blue protective foil and instantly deposit the POSITIV photoresist.

• Put the glass into spincoater and run the PROGRAM 4 (600rmp/30s ; 2000rpm/30s).

• Leave in petry-dish for some minutes letting fotorezist to dry.

• Bake the photoresist for 45-60 min at 50°C.

• Exposure the photoresist over mask. The exposure time was established to 4 min for solid mask and 6.5 min in case of foil mask. For both cases the mask should be placed at 4cm distance from the UV fluorescent tube.

• Develop the exposed photoresist in 0.7% NaOH.

• Etch the ITO layer in 5% HCl acid (5g 30% HCl + 25g H2O) for 1 min 20 sec. It is possible to remove substrate from the acid during etching process and check it under microscope or test the conductivity of etched areas to avoid over-etching.

• Remove the resulting photoresist washing in IPA.