Vertically Stacked CMOS-Compatible Photodiodes for Scanning Electron Microscopy

This paper reports the use of vertically stacked photodiodes as compact solid-state spectrometers for transmission scanning electron microscopy. SEM microscopes operate by illuminating the sample with accelerated electrons. They can have one or more solid-state sensors. In this work we have tested a set of stacked photodiodes fabricated in a standard 180nm HV-CMOS technology without process modifications. We have measured their sensitivity to electron irradiation in the energy range between 10keV and 30keV. We have also assessed their radiation hardness. The experiments are compared with Monte Carlo simulations to investigate their spectral sensitivity.