The time-dependent charging process of an insulating specimen under electron beam irradiation is calculated by taking into account the charge continuity equation, the Poisson equation, Ohm's law and the electron-beam-induced conductivity. The energy and the charge deposition distributions are calculated by the Monte Carlo simulation of electron trajectories taking into account the electric field distribution in the specimen. The time-dependent charge and potential distributions are obtained in the present calculation. As the electron beam energy is 10 keV and the specimen is a 1-mm-thick poly-methyl-methacrylate (PMMA) wafer, the surface potential increases to a positive value at first, and then becomes a negative one. This charging process agrees with experimental findings.

A new Monte Carlo calculation model is presented to simulate not only the primary electron behavior but also the secondary electron cascade in a specimen bombarded with an electron beam. Electrons having energy greater than 0.1 keV are treated as ‘‘fast electrons’’ and the previous single scattering Monte Carlo model is adopted. Electrons having energy smaller than 0.1 keV are treated as ‘‘slow electrons’’ and the electron cascade Monte Carlo model is used. The calculated results for the energy distribution of secondary electrons, and primary electron energy dependence of the total secondary yield and the backscattering yield are in good agreement with experimental results.

No abstract

Supposing that an insulator is charged-up negatively by an accumulation of incident primary electrons, we study how much the subsequent incident electron is influenced by the charge in the specimen. We introduce a new Monte Carlo simulation model of electron scattering in a solid taking into account an electric field around the simulated electron. In a present study the incident electron energy is 20 keV, and the insulator is a poly-methyl-methacrylate wafer of 1 mm in thickness. This paper clarifies the changes in some physical quantities, e.g., the backscattering coefficient, energy deposition, etc. due to the specimen charging during an electron beam irradiation.