An optimization method for nonequiradial electrostatic deflection systems

Electrostatic deflectors are very important elements in electron and ion beam equipment. The improvement of their characteristics can be achieved by a nonequiradial arrangement of the deflection electrodes. A graphical method for determining the parameters of nonequiradial deflectors based on the known integral equation method is developed. The geometrical parameters of the deflection electrodes are represented by a certain number of infinitely long charged 'bars'. The nonequiradial position of the correcting electrodes with respect to the main deflecting electrodes allows the individualization of 8-pole deflectors in electron lithographs as subfield and full scale deflectors. The proposed nonequiradial arrangement of electrodes can increase the sensitivity of 12-pole deflectors. (author)