we don't have a UV photolithography system. But we have a 405nm direct laser writer But we are not able to pattern SU8 of thickness 20 microns, even by using multiple exposures. Is there any way to do this pattern by using a laser writer?
It might be possible that the laser power is low or lacking in proper focusing on the sample. Increase the power of the laser and tightly focus on the sample using a high numerical aperture objective lens. You can also use a femtosecond laser to do the same. Many papers are available on the same using femtosecond laser.
Hope it will help you.
What kind of SU-8 are you using? Most of them are only i-line sensitive and g/h line exposure is at least cumbersome due to low absorbance. Have you tried broadband SU-8 TF6000? https://kayakuam.com/products/su-8-tf-6000/
Dear Bobby Bnm, maybe you are applying a thick layer of photoresist? You can learn a lot about U-8 photoresist properties and resolution from https://en.wikipedia.org/wiki/SU-8_photoresist.
I think that the sensitivity of the photoresist at 405 nm is very low.
Best regards, Vladimir Shapar.
Hi Bobby, we have 405nm direct laser writer. We tested SU8 with 10um thickness. To have sufficient results, you need to use 100% laser power, no filter and run many (at least 3) litoghraphic processes in the same point
For lesser thickness we can use laser 405nm with 100percent filter. If you want to try for higher thickness ,you need to give multiple doses at same point. This will take huge time to pattern complete design.
To expose SU-8 photoresist you need to have photons with sufficient energy to produce the proton from the photo acid generator molecule. The light you need has to have i-line (365nm) or shorter wavelengths. Using 405nm wavelength will do nothing. This is like the photoelectric effect, intensity does not matter, energy of the photons matters. The photon must have sufficient energy to bring the molecule over the activation energy barrier.
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