Department of Physics, Faculty of Sciences, BP 1039, 51687 Reims Cedex 2, France.
Ultramicroscopy. 2010 Feb;110(3):242-53. doi: 10.1016/j.ultramic.2009.12.002. Epub 2009 Dec 23.
'Is it possible to assign various grey levels of a scanning electron microscope (SEM) image to different components of a given sample? Among other instrumental effects, the answer is not only a function of the respective secondary electron emission (SEE) yields of the components, delta, but also of the angular fraction of the secondary electrons (SE)s being collected, k(alpha) and of a possible voltage contact effect between sample and detector, k(varphi). Expressed as a function of E(F), Fermi energy, and varphi, work function of the components of interest, equations of spectral, ( partial differentialdelta/ partial differentialE(k)), and angular, ( partial differentialdelta/ partial differentialalpha) distributions of the emitted SEs permit to evaluate k(alpha) and k(varphi) for Au and Si. It has been established that collected SE spectra, partial differentialdelta(alpha)/ partial differentialE(k), are distorted with respect to the emitted and fraction k(alpha) is material dependent for a solid angle of detection Omega degrees less than 2pi (or maximum semi-apex angle alpha(max)<90 degrees ) In particular, for coaxial detections around the normal incident beam the detected fraction of SEs from Au, k(alpha)(Au), is slightly larger than that for Si, k(alpha)(Si). For simple geometries in the vacuum gap, similar investigations show that parameter k(phi) is also larger for gold than for n-doped Si as well as for p-doped Si with respect to n-doped Si. Then Au is always quite brighter than n-doped Si in the SEM images while a doping contrast, C, due to a work function effect may reach approximately 15% for a Si p/n junction with N(p) approximately 10(16) and N(n) approximately 10(15)cm(-3). The present analysis may be extended to some metals such as Ag, Cu, Pb, Pd, Pt, and Zn that are expected to appear brighter than Si(n) and Ge in the SEM images. The influence of specimen surrounding in the vacuum gap and of detection conditions are outlined. The limitations of present approach are discussed and a strategy is suggested for the investigation of electronic devices where these components are in reduced number and are known a priori.
是否可以将扫描电子显微镜（SEM）图像的不同灰度级别分配给给定样品的不同成分？除了其他仪器效应外，答案不仅取决于各个成分的二次电子发射（SEE）产率δ，还取决于收集的二次电子（SE）的角分率 k（alpha）以及样品和探测器之间可能的电压接触效应 k（varphi）。表示为 E（F），费米能和感兴趣成分的功函数 varphi 的函数，发射 SE 的光谱（偏微分δ/偏微分E（k））和角度（偏微分δ/偏微分alpha）分布的方程允许评估 Au 和 Si 的 k（alpha）和 k（varphi）。已经确定，收集的 SE 光谱，偏微分δ（alpha）/偏微分E（k）相对于发射和分率 k（alpha）相对于检测立体角 Omega 度小于 2pi（或最大半顶角 alpha（max）<90 度）失真，特别是对于围绕正常入射束的同轴检测，从 Au 检测到的 SE 分率 k（alpha）（Au）略大于 Si，k（alpha）（Si）。对于真空间隙中的简单几何形状，类似的研究表明，对于 n 掺杂 Si 以及相对于 n 掺杂 Si 的 p 掺杂 Si，金的参数 k（phi）也大于金。因此，在 SEM 图像中，Au 总是比 n 掺杂 Si 亮得多，而由于功函数效应引起的掺杂对比度 C 对于具有 N（p）约为 10（16）和 N（n）约为 10（15）cm（-3）的 Si p/n 结可能达到约 15％。本分析可以扩展到一些金属，如 Ag，Cu，Pb，Pd，Pt 和 Zn，它们预计在 SEM 图像中比 Si（n）和 Ge 更亮。概述了真空间隙中样品周围和检测条件的影响。讨论了目前方法的局限性，并提出了一种策略，用于研究其中这些成分数量较少且事先已知的电子器件。
