20210621 photolitho

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  • Opened new package of 4" wafers
  • Plasma treated + 15 min+ @135C
  • SU8 spread 60s@600rpm, then 40s@1700rpm for 50 um
  • Both wafers have several holes in su8 layer, I do ont know if this is due to dirt/dust on wafers or tiny air bubbles in SU8. 2nd wafer I tried to mend initial holes, but it did not help.
  • Not much SU8 left in syringe, maybe that is whey there were air bubbles? Removed stock bottle from fridge to replenish SU8 in syringe before end of day.
  • 11:15 prebake started on VWR hotplate
  • One of the wafers had completely irregular SU8, useless!! The other had several holes, but some usable areas. => we need to clean the wafers!!
  • Exposure: 34s@25% intensity = 400 mJ/cm^2
  • Post-bake 15min@65C, 40min@95C
  • Development: small holes did not develop