Angle-energy analyzers of back-scattered electrons for layer-by-layer diagnostics of microelectronics devices in Scanning Electron Microscope

In previous work it was shown that it was possible to visualize depth microstructure of solidstate samples in layer-by-layer form using some modifications of the back-scattered electron (BSE) detector system in the scanning electron microscope. The approach is based on the idea to detect not all of the BSE current, but only the part of it with the directions of velocities close to inverse to the primary beam and energies within a small window in the high-energy part of the whole spectrum. The fact is that when primary electrons scatter in sample, consisting only of light elements, the process of their elastic scattering can be formally divided on two-parts: small-angle scattering and large-angle scattering. In this case the probability of small-angle scattering is approximately five orders higher than large-angle scattering. Taking into account that energy of an electron can be considered as decreasing continuously, if an electron scatters in a sample and comes out with the velocity mentioned above, one can say, that it most probably passed exactly one large-angle scattering in a sample media.