Design and evaluation of an electron objective lens system with two lenses and two deflectors

In order to improve the performance of an electron beam lithography system, the objective lens system plays a key role. In multi-deflection systems, aberrations can be theoretically decreased by increasing the number of optical elements. From the viewpoint of practical design, however, the number of elements should be as small as possible because error in their manufacturing causes aberrations. The deflector is the most critical element because its manufacturing error can occur easily. We have thus investigated practical aberrations of a two-deflector objective lens system.