Contrast mechanism due to interface trapped charges for a buried SiO2 microstructure in scanning electron microscopy

We clarify the scanning electron microscopic contrast mechanism for imaging a buried SiO2 trench microstructure with interface trapped charges by simulating both electron scattering and transport. Here, the interface trapped charges make the SiO2 film more negatively charged and increase excess holes in the space charge distribution of the electron scattering region. The generated positive surface electric field thus redistributes some emitted secondary electrons and results in the dark contrast. This contrast mechanism is validated by comparing with experiments, and it may also provide an interesting approach for imaging and detecting deep interface trapped charges in insulating films.