Direct Laser Writing (DLW)

KNMF Laboratory for Micro- and Nanostructuring

DLW principleWith DLW resist 2D-patterns in the µm-range are written in a photo resist layer on a substrate with a focused laser beam. No mask is needed as in conventional photo lithography.

The writehead allows feature sizes down to 2.5 µm with a substrate size up to 6”. The machine complements E-Beam lithography and is a less expensive and faster alternative for structures without nano sized features. Typically this method is applied to generate first prototypes and allows a faster iteration.

Due to the used wavelength of 355 nm it is possible to pattern thicker resist layers (e.g. SU-8 type resists). The focusing of the laser beam leads in this case to sloped sidewalls (< 5°).

In case of reflective substrates a bottom antireflection coating (BARC) has to be applied, which may be considered in the whole process layout.

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Details (DLW)


  • Heidelberg Instruments DLW66 fs
  • Writehead 10 mm and 4 mm (lower and higher resolution)


  • No mask needed
  • The wavelength of the Laser (355 nm) allows to expose SU-8-Resist up to 300µm thickness and AZ-Resists up to 7µm thickness.
  • Writing speed is 35 mm²/min. A 4“ wafer will be written in round about 3 hours.


  • The structure sidewalls are not vertical in case of thicker resist layers
  • Aspect ratios up to 4 are possible depending on structures and/or resists


  • Resists: AZ1505, AZ4533, SU8 and similar resists
  • Substrate properties:
    - flat
    - roughness peak to peak < 80 µm
    - 100 µm < thickness <  2500 µm


  • Data File format: gds-II, dxf (2D), cif
  • To work with good files the following hints are very useful:
    - closed polylines should be used
    - layers should not be named "main"
    - define proper scale before designing your pattern
    - use appropriate number of points in polygon approximation

Structure examples

DLW examples