Origination by Interference Lithography

In Fig. 11, a sketch of the optical set-up for interference lithography and in Fig. 12, a picture of the largest interference lithography laboratory at Fraunhofer ISE are shown. A laser beam is split, directed with mirrors and then spatially filtered and expanded. A sample holder with the photoresist plate is positioned where the expanded beams are superimposed. A shutter defines the exposure time. Behind the spatial filters, no optical components are in the optical path in order to avoid parasitic interference effects such as Airy patterns from dust particles. The nonplanarity of the interfering beams results in a small variation of the grating periods which is tolerated for the above mentioned appfications. If one assumes symmetrical angles of incidence a, then the 

Structuring large areas requires large distances from the spatial filters to the photoresist plate in order to maintain the period variation of the photoresist structure 

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F. 10 Cross section of a microprism substrate with a structure period of 20pm originated by interference lithography, carrying a microgrid and coated with the polymer anode (SEM image)... 

Fig. 12 SEM pictures of two microstructures which were originated by interference lithography (a) prism array structure in photoresist, (b) replica of a CPC array in poly(methyl methacrylate) (PMMA) partly coated with metal...

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