Are you seeing iregularly shaped circular features when writing RAITH circles?

[James Conway]

Greetings Raith Community:

Several users have reported that their Photonic Crystal circles written 
with RAITH circle function have been elliptical or not completely 
cleared out on positive PMMA resist.
  I am working with several users on this and may have identified two 
trends that could result in this phenomenon.

1. Beam speeds are allowed to be too high!! Be sure to inspect your 
exposure window and ensure that the area write and line write beam 
speeds are below 10 mm / second.  This is to ensure you do not 
experience fly back effects as the data arrives to the deflection system 
before the beam reached it proper position.   This is likely a result of 
using old parameters and aperture selections with the new improved Beam 
current we achieved after the recent PM.  Features written in the X 
direction will become elongated, circles become ovals.

2. Area steps are too big!! Note that the area step parameter is 
employed to place the RAITH single pixel line (SPL) in the pattern 
written in RAITH circle mode.  This will result in shots that do not 
connect or overlap during your EBL write.
Features written will have very rough line edge roughness and have an 
appearance of swiss cheese or closed area of your circles.

Other users observing this or other strange write results are requested 
to report to this list and include measurements and images if possible.  
You may stop by during my office hour as well.

Thank you for your support!

James Conway