Sources of Dark Current in Backscattered Electron Detectors and a Novel Multiple Guard Ring Design to Lower It

Backscattered electron detector (BSD) is a key component in electron-based microscopies. To achieve a high-performance BSD, in other words, a detector with high signal-to-noise ratio, minimizing the dark current is crucial. In this study, the dark current of BSD was systematically investigated considering the impact of surface damages, contamination, and moisture. To reduce the dark current, a novel multiple guard ring structure is proposed and optimized, taking into account parameters including the width of guard ring and gaps between the active area and guard rings. Compared to the commonlyused single guard ring structure, the simulated results indicate that the proposed multiple guard ring structure effectively decreases the dark current to 0.25 nA/cm
²
, while the breakdown voltage increases to 930V.