Electron ray tracing with high accuracy

An electron ray tracing program is developed to investigate the overall geometrical and chromatic aberrations in electron optical systems. The program also computes aberrations due to manufacturing errors in lenses and deflectors. Computation accuracy is improved by (1) calculating electrostatic and magnetic scalar potentials using the finite element method with third‐order isoparametric elements, and (2) solving the modified ray equation which the aberrations satisfy. Computation accuracy of 4 nm is achieved for calculating optical properties of the system with an electrostatic lens.