Photolithography

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Photolithography explained

Photolithography

SU8 process (square features)

Procedure updated Nov 2023

Handling of chemicals

Preparations the day before photolithography

  • Open a new lab note here
    • Note down your desired process
    • As you go on the day, note all observations and final result
  • Decide how thick layer of SU8 you need
  • Choose right SU8 and protocol
  • Find and note the following parameters (See page with tables and notes on parameters):
    • Speed of spin-coater in rpm
    • Pre- and post-bake times at 65 and 95 C, t_{65}, t_{95}
    • Exposure dose (divide the number from the table by factor 2 to 4, follow Mathias' measurement, use 20% power and multiply the time by 5)
    • PGMEA development time
  • Take SU8 out of fridge and place in cupboard in 129
  • Program

Materials and tools

  • SU8
  • Wafer (3" or 4")
  • Isopropanol
  • Wafer tweezers (in LAF bench and fume hood)
  • Fine tipped tweezer
  • Clean glass plate for placing wafers on
  • N2 guns in 128 and 129
  • Beaker and wafer holder for development
  • Lint free paper

Procedure

  • Turn on N2
  • Turn on and open LAF bench


  • Turn off N2
  • Turn off and close LAF bench

Procedure notes before Nov 2023

Programming various equipment

UV KUB programming

Spin coater programming

Hot plate programming

Important notes 05.03.2021

  • UV doses in the tables are too large. Look at comments in Matias Busek's protocol
  • The programmable hotplate is not reliable
    • Two times in a row the same procedure for 25 um thick substrate with VWR and programmable hot plates gave good results for VWR hotplate but overdevelopment for programmable hotplate.
    • I have observed that the programmable hotplate seems to spend too long time at each step.

XT process (rounded channels)