Transmission electron microscope (TEM) specimen preparation by focused ion beam (FIB) milling requires delicate polishing of a thin window of material during the final stages of the procedure. Over- or under-polishing is common and requires extra microscope resources to correct. Despite some methods for lamella thickness measurement being available, the majority of users judge the final polishing step subjectively from scanning electron microscope (SEM) images acquired between milling steps. Here we demonstrate successful thickness determination of thin silicon lamellae using calibrated secondary electron detectors in a FIB-SEM dual-beam chamber. Unlike previous thickness measurement methods it does not require long acquisition times, the use of in-chamber scanning transmission electron microscope (STEM) or energy dispersive x-ray spectroscopy detectors. The calibration aligns a SEM image to an electron energy loss spectroscopy (EELS) map of lamella thickness acquired in a TEM. This calibration reveals the greyscale-thickness dependence of two secondary electron SEM detectors: the through-lens detector (TLD) and the in-chamber electron detector (ICE). It was found that lamella thickness estimation for TLD images is accurate for areas thinner than 0.4 t/λ, whilst ICE images are most accurate for areas thicker than 0.5 t/λ up to 1.1 t/λ. The procedure presented here allows objective lamella thickness determination during the final stages of FIB specimen preparation using conventional imaging modes for common secondary electron detectors. This article is protected by copyright. All rights reserved.

中文翻译：

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在 FIB-SEM 中直接测量 TEM 薄片厚度

通过聚焦离子束 (FIB) 铣削制备透射电子显微镜 (TEM) 样品需要在该过程的最后阶段对材料的薄窗进行精细抛光。过度抛光或抛光不足很常见，需要额外的显微镜资源来纠正。尽管有一些测量薄片厚度的方法可用，但大多数用户根据铣削步骤之间获得的扫描电子显微镜 (SEM) 图像主观判断最终抛光步骤。在这里，我们展示了在 FIB-SEM 双束室中使用校准的二次电子探测器成功测定薄硅片层的厚度。与以前的厚度测量方法不同，它不需要很长的采集时间，使用室内扫描透射电子显微镜 (STEM) 或能量色散 X 射线光谱检测器。校准将 SEM 图像与在 TEM 中获得的薄片厚度的电子能量损失光谱 (EELS) 图对齐。该校准揭示了两个二次电子 SEM 检测器的灰度-厚度依赖性：通过透镜检测器 (TLD) 和室内电子检测器 (ICE)。结果表明，TLD 图像的薄片厚度估计对于小于 0.4 t/λ 的区域是准确的，而 ICE 图像对于厚度大于 0.5 t/λ 至 1.1 t/λ 的区域最准确。此处介绍的程序允许在 FIB 样品制备的最后阶段使用常见二次电子探测器的常规成像模式进行客观薄片厚度测定。本文受版权保护。