Electron-beam-generated carrier distributions in semiconductor multilayer structures

The electron beam of a scanning electron microscope causes carrier generation in a semiconductor and these carriers are the probe for various types of image. In particular, the electron-beam-induced current mode gives images which reveal electrically active near-surface defects in a semiconductor sample. Since semiconductor multilayer structures are now very common, one needs to know how the multilayer structure modifies the shape of the generation volume. The Monte Carlo technique for modelling beam electron trajectories inside the sample is used and gives a detailed insight into the shape of such a generated carrier generation distribution. Additionally, a simpler analytical method is developed for constructing a one-dimensional depth distribution for multilayer structures, starting from known depth dose distributions for bulk materials. The analytical method is validated by comparison with Monte Carlo results.