News and Reviews (November 2014)

Maskless Lithography

2D manufacturing by direct laser writing

(Yann Tanguy, Fabian Niesler) While known for its outstanding 3D printing capabilities, the Photonic Professional GT system also enables high-resolution 2D patterning of thin films, called maskless lithography.
The technology of direct laser writing (DLW) complements 2D manufacturing technologies available on the market and represents an alternative to traditional electron-beam lithography (EBL) and photolithography technologies offering similar performance levels. In terms of spatial resolution, a recent publication [1] positions DLW between these two technologies, while the patterning speed is now approaching EBL standards thanks to the implementation of galvanometric mirror scanners. 2D photoresist structuring using a DLW approach does not require expensive masks which makes it an ideal tool for all aspects of prototyping applications as well as fabrication of masters.

The underlying principle of two-photon absorption combines high resolution patterning together with a broad range of compatible UV sensitive photoresists. Structures with high-aspect ratios can be achieved without limitations from Beer’s absorption law or electron scattering effects. Along the list of compatible negative-tone photoresists are SU-8 as well as Nanoscribe’s IP resins that provide robust and reliable process results.  
Nanoscribe has recently evaluated the performance of the Photonic Professional GT for 2D patterning of various thin- and thick-film positive tone resists of the AZ® series [2] (AZ® 9260, AZ® 5214E, AZ® MIR 701, AZ® 40XT) on glass and silicon substrates. These resists and substrates cover a broad range of application fields, e.g. etch masks, sputter masks, high-aspect ratio structures and electro-plating templates.

[1] D.S. Engstrom et al., „Additive nanomanufacturing – A review“, J. Mater. Res., 2014.   
[2] These resists are available off the shelf from

silicon-wafer.jpg SN486-job213-38_az9260.jpg

left: Checkerboard arrangement of test patterns fabricated in positive-tone resist AZ® 5214 on 4 inch silicon wafer.
right: Zoom-in on high-aspect-ratio grating fabricated in thick positive-tone resist AZ® 9260.

SEM micrographs of various 2D patterns in positive and negative tone photoresists fabricated with a
Photonic Professional GT.