High efficiency secondary electron detection for the electron-beam-reducing projection lithography system

The secondary electron (SE) trajectories are calculated for two cases, in which the axial magnetic field from the projection lens at the target is zero and not zero. In the former case, SEs are easily detected by the SE detector, which is placed distant from the optical axis. For the latter case, it is difficult to detect SEs. The reasons are dear because, for the former case, the magnetic Aux never crosses the target plane, and for the latter case, most of the magnetic flux crosses the target plane, and SEs with relatively small initial SE energy (E-i) tend to travel along the magnetic nux. When an axially symmetric electrostatic field whose potential at the optical axis is 0.35 V, for the maximum E-i of 30 eV and the emission angle of 30 degrees, and for the E-i of 3 eV and the maximum emission angle of 89 degrees, all the SEs are detected by the SE detector.