Bok Jan, Schauer Petr
Institute of Scientific Instruments of the ASCR, v.v.i., Brno, Czech Republic.
Scanning. 2014 Jul-Aug;36(4):384-93. doi: 10.1002/sca.21130. Epub 2013 Dec 3.
In the paper, the SEM detector is evaluated by the modulation transfer function (MTF) which expresses the detector's influence on the SEM image contrast. This is a novel approach, since the MTF was used previously to describe only the area imaging detectors, or whole imaging systems. The measurement technique and calculation of the MTF for the SEM detector are presented. In addition, the measurement and calculation of the detective quantum efficiency (DQE) as a function of the spatial frequency for the SEM detector are described. In this technique, the time modulated e-beam is used in order to create well-defined input signal for the detector. The MTF and DQE measurements are demonstrated on the Everhart-Thornley scintillation detector. This detector was alternated using the YAG:Ce, YAP:Ce, and CRY18 single-crystal scintillators. The presented MTF and DQE characteristics show good imaging properties of the detectors with the YAP:Ce or CRY18 scintillator, especially for a specific type of the e-beam scan. The results demonstrate the great benefit of the description of SEM detectors using the MTF and DQE. In addition, point-by-point and continual-sweep e-beam scans in SEM were discussed and their influence on the image quality was revealed using the MTF.
在本文中，通过调制传递函数（MTF）对扫描电子显微镜（SEM）探测器进行评估，该函数表示探测器对SEM图像对比度的影响。这是一种新颖的方法，因为MTF此前仅用于描述面积成像探测器或整个成像系统。文中介绍了SEM探测器MTF的测量技术和计算方法。此外，还描述了作为SEM探测器空间频率函数的探测量子效率（DQE）的测量和计算。在该技术中，使用时间调制电子束为探测器创建定义明确的输入信号。在Everhart-Thornley闪烁探测器上展示了MTF和DQE测量结果。该探测器使用YAG:Ce、YAP:Ce和CRY18单晶闪烁体进行了交替测试。所呈现的MTF和DQE特性表明，使用YAP:Ce或CRY18闪烁体的探测器具有良好的成像性能，特别是对于特定类型的电子束扫描。结果证明了使用MTF和DQE描述SEM探测器的巨大优势。此外，还讨论了SEM中的逐点和连续扫描电子束扫描，并使用MTF揭示了它们对图像质量的影响。
