Dynamic simulation of secondary electron emission and charging up of an insulating material

The charging up induced by electron bombardment of SiO2 is studied by using a self-consistent Monte-Carlo simulation of the transport of a primary electron and secondary electrons (SE) and the generation of an electric field due to the charges in the material. The calculation is compared with an experiment using electron beams on charging up of an oxide layer on Si. The transient behavior of SE yield and surface voltage is calculated. In a surface layer, positive charges dominate the space charge distribution, whereas the electrons brought back by an external electric field distribute on the top surface. For low beam energies (< 100 eV), the charge distribution reaches deep regions (~ 50 nm) over the beam penetration depth (~ 5 nm) due to the drift by following an internal electric field.