Online Beam Current Estimation in Particle Beam Microscopy
Online Beam Current Estimation in Particle Beam Microscopy
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DOI：
10.1109/tci.2022.3182212
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发表时间：
2021-11
影响因子：
5.4
通讯作者：
Sheila W. Seidel;Luisa Watkins;Minxu Peng;A. Agarwal;Christopher C. Yu;V. Goyal
中科院分区：
文献类型：
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作者：
Sheila W. Seidel;Luisa Watkins;Minxu Peng;A. Agarwal;Christopher C. Yu;V. Goyal
在传统的粒子束显微镜中，了解束流对于精确的显微图像形成和样品铣削至关重要。这通常需要对仪器进行离线校准。在这项工作中，我们确定可以根据用于形成显微照片的相同二次电子计数数据在线估计束电流。我们的方法依赖于最近引入的时间分辨测量概念，该概念结合了单个像素的多个短测量，并且之前已被证明可以部分减轻束电流变化对显微照片精度的影响。我们分析了使用 Cramér-Rao 界限联合估计束流和二次电子产额的问题。提出了在单个像素上运行的联合估计器和利用像素间相关性和马尔可夫束电流变化模型的估计器，并在合成显微镜数据上进行了测试。我们对二次电子产率的估计结合了明确的束流估计，击败了最先进的方法，导致显微照片的准确性与完美束流知识所获得的结果几乎没有区别。我们新颖的束流估计可以帮助改善研磨结果、防止样品损坏并实现在线仪器诊断。
In conventional particle beam microscopy, knowledge of the beam current is essential for accurate micrograph formation and sample milling. This generally necessitates offline calibration of the instrument. In this work, we establish that beam current can be estimated online, from the same secondary electron count data that is used to form micrographs. Our methods depend on the recently introduced time-resolved measurement concept, which combines multiple short measurements at a single pixel and has previously been shown to partially mitigate the effect of beam current variation on micrograph accuracy. We analyze the problem of jointly estimating beam current and secondary electron yield using the Cramér–Rao bound. Joint estimators operating at a single pixel and estimators that exploit models for inter-pixel correlation and Markov beam current variation are proposed and tested on synthetic microscopy data. Our estimates of secondary electron yield that incorporate explicit beam current estimation beat state-of-the-art methods, resulting in micrograph accuracy nearly indistinguishable from what is obtained with perfect beam current knowledge. Our novel beam current estimation could help improve milling outcomes, prevent sample damage, and enable online instrument diagnostics.