I am trying to fabricate some silicon pillars with different radiuses on SOI exploiting an Ebeam lithography with 30KV. I already tried different photoresists including PMMA, Ma-N, and SU8 to make a pattern on SOI but yet it didn't work properly. The issue is that the pillars are so close to each other (periodicity 190nm) that the backscattering is affecting other adjacent parts and the result is not good enough for the next step which is RIE etching. I was wondering to ask the experts how can I manage to make these features on such a scale using a different fabrication approach or photoresist...
You can try the following things:
1) You can try to limit the no of electrons falling on the sample (current) by reducing the aperture size. This normally improves the resolution but at the cost of an increase in writing time.
2) Please make sure that your beam is focussed very well (as good as you can), this you can try by burning a spot in the unused area at higher magnification and then zooming out to see if you get a good circle and not oval in shape.
3) You can also try to decrease the thickness of the resist, it helps in writing smaller structure.
Please let me know if this is helpful.
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