高分辨二次电子像中的成分衬度

从理论上阐明了获得高分辨二次电子成分衬度像的原理、条件和方法，并作了细致的实验验证，空间分辨率为３．３ｎｍ（Ｖ０＝５ｋＶ），原子序数分辨率为０．０３Ｚ。实验研究样品为分子束外延ＡｌＧａＡｓ量子阱激光器，其分层结构的最小层宽为７ｎｍ，测得的层宽和透射电镜测量结果相吻合，由于透射电镜制样的复杂和困难，高分辨扫描电镜二次电子成分衬度像观测方法具有重要的理论意义和实用价值     

高分辨二次电子像中的成份衬度

高分辨二次电子像中的成份衬度徐军陈文雄张会珍（北京大学电镜实验室，北京１００８７１）在传统的扫描电子显微学的概念中，二次电子像中包含的是形貌衬度，而背散射电子像中包含的是成份衬度。但实际上二次电子的产额是和样品的成份有关的，不过样品表面极易玷污，样品...     

PVT生长掺V SiC单晶的扫描电镜二次电子像衬度

在用SEM观察沿单晶生长方向切割掺V SiC晶片时,发现其二次电子像存在衬度。表现为先生长部分较明亮,后生长部分较暗淡,中间存在明显突变。在用PVT生长掺V SiC单晶时,SiC单晶中同时含有浅施主N和深受主杂质V是补偿半导体。从补偿半导体载流子浓度计算出发,建立了二次电子像衬度与载流子浓度的对应关系,很好解释了这一实验现象。结果表明,SiC单晶生长过程中随着浅施主N的减少,n型载流子的浓度逐步减少;当其浓度与V相当时,载流子浓度突变,可瞬间减少10个量级,此后又缓慢减少。正是这种载流子的突变引发了扫描电镜二次电子像衬度。     

半导体二次电子像中的掺杂衬度

本文详细评述和介绍了近几年来国际上关于扫描电镜二次电子像中的掺杂衬度方面的实验和理论研究成果，总结了实验中发现的各种现象，并用电离能的观点对所有这些现象作出了理论上的解释，并指出了这种技术的应用前景。     

高分辩二次电子像中的成分衬度

从理论上阐明了获得高分辩二次电子成分衬底像的原理，条件和方法，并作了细致的实验验证，空间分辩率为３．３ｎｍ，原子序数分辩率为０．０３Ｚ。实验研究样品为分子束外延ＡｌＧａＡｓ量子阱顺，其分层结构的最小层宽为７ｎｍ，测得的层宽和透射电镜测量结果相吻合，由于透射电镜制样的复杂和困难，高分辩扫描电镜二次电子成分衬度像观测方法具有重要的理论意义和实用价值。     

聚焦偏转复合系统像差分析及应用

介绍了以DX-3扫描电镜为基础，利用SDS-2电子束扫描系统改装其偏转系统。并给出了磁聚焦和静电的偏转场相复合情况下竖轴点源的三级几何像差系数和一级色差系数公式。应用中表明，复合系统结构简单紧凑，像差小而可以不用动态校正。     

绝缘膜负带电时的表面局部电场与二次电子返回特性

为分析IC多层版图扫描电镜(SEM)对准检测所利用的负带电成像原理,采用Mott弹性散射截面和修正的Bethe非弹性碰撞公式,对点照射入射电子在绝缘膜中的散射过程进行了Monte Carlo模拟,得到负带电绝缘物表面的局部电位分布.在此基础上计算了二次电子从表面出射后在局部场作用下的运动轨迹,获得了SEM像的二次电子信号电流.结果表明,在弱负带电条件下,照射点处表面电位越低,返回表面的二次电子就越多,对应的二次电子信号电流越弱.此结果与SEM实验中图像亮度随照射时间的变化规律相符.     

绝缘膜负带电时的表面局部电场与二次电子返回特性

为分析IC多层版图扫描电镜(SEM)对准检测所利用的负带电成像原理,采用Mott弹性散射截面和修正的Bethe非弹性碰撞公式,对点照射入射电子在绝缘膜中的散射过程进行了Monte Carlo模拟,得到负带电绝缘物表面的局部电位分布.在此基础上计算了二次电子从表面出射后在局部场作用下的运动轨迹,获得了SEM像的二次电子信号电流.结果表明,在弱负带电条件下,照射点处表面电位越低,返回表面的二次电子就越多,对应的二次电子信号电流越弱.此结果与SEM实验中图像亮度随照射时间的变化规律相符     

电压衬度像技术在IC失效分析中的应用

电压衬度像(PVC)技术是用于定位集成电路不可见缺陷的一种有效的失效分析方法,结合聚焦离子束(FIB)精准的微切割技术,可将PVC技术应用于长金属互连线的缺陷定位.主要介绍了PVC技术及其原理,概述了如何在SEM和FIB中应用其工作原理有效地定位IC缺陷位置,并就接触孔/通孔缺陷以及规则长金属导线的失效实例展开讨论和分析.     

透射电子显微学的新进展ⅡZ衬度像、亚埃透射电子显微学、像差校正透射电子显微学

本文综述了原子分辨率的原子序数衬度成像与原位电子能量损失谱分析、亚埃透射电子显微学、像差校正透射电子显微学和材料的微观结构表征与原位性能测试的最新发展和应用。在配置球差校正器、单色器和高能量分辨率过滤器的FEGTEM／STEM中,用相位衬度像／Z衬度成像与原位电子能量损失谱分析方法,在亚埃的空间分辨率和亚电子伏特能量分辨率下,可以研究各种材料的原子尺度界面和缺陷的原子和电子结构、价态、成键和成分等。配置球差校正器后,可明显提高透射电镜的点分辨率,把点分辨率延伸到信息分辨率,同时显著减小村度离住。随意改变球差系数Cs和离焦值△f,像差校正透射电子显微镜可提供新的成像模式。把特殊的样品杆插入电镜后,可把扫描隧道显微镜(STM)或原子力显微镜(AFM)功能相结合,开展材料的显微结构表征与原位的性能测试,不仅能得到物质的与显微像、成分、衍射有关的信息,同时还可以测量电学、力学性能,也可以研究在外场(温度、应力、电和磁场)作用下材料微观结构演变及结构与性能间的关系。     

二次雾霾气溶胶颗粒的扫描电子显微学分析

北京地区的雾霾是全国,也是世界都在关注的问题.作者利用高分辨环境扫描电镜结合能谱仪,分析了雾霾气溶胶颗粒中的硫酸盐和硝酸盐等典型二次反应颗粒的形貌特征、化学成分、可能的物相及它们的混合态.结果表明:二次颗粒的尺寸为数纳米至数微米.它们呈多种形态,包括梭形、条状、球形、柱状、针状、片层状等.几种二次颗粒之间,以及二次颗粒与天然矿物尘及其它人为来源的飞灰和金属基颗粒等经常形成颗粒间粘附的混合颗粒团聚体.     

An electron image projector with automatic alignment

An electron image projector for silicon device processing is described which uses an air-cored solenoid and a caesium iodide photocathode. The alignment method is based on the X-rays which are generated when high-voltage electrons strike matter. Phase sensitive detection is used to convert the off balance to a linear signal which is then fed back into analog electronics. Results are presented showing a marker pattern automatically aligned to an accuracy of 0.1 µm.     

Quantitative characterization of electron micrograph image usingfractal feature

In this investigation, texture analysis was carried out on electron micrograph images. Fractal dimensions and spatial grey level co-occurrence matrices statistics were estimated on each homogeneous region of interest, The fractal model has the advantages that the fractal dimension correlates to the roughness of the surface and is stable over transformations of scale and linear transforms of intensity. It can be calculated using three different methods. The first method estimates fractal dimension based on the average intensity difference of pixel pairs. In the second method, fractal dimension is determined from the Fourier transformed domain. Finally, fractal dimension can be estimated using reticular cell counting approach. Moreover, automatic image segmentation was performed using fractal dimensions, spatial grey level co-occurrence matrices statistics, and grey level thresholding. Each image was segmented into a number of regions corresponding to distinctly different morphologies: heterochromatin, euchromatin, and background. Fractal dimensions and spatial grey level co-occurrence matrices statistics were found to be able to characterize and segment electron micrograph images     

In-the-lens secondary electron analyser for IC internal voltage measurements with electron beams

A new analyser scheme for voltage measurements on integrated circuits is described. The analyser is built into the objective lens of a scanning electron microscope. It features small working distances, high voltage resolution capability, high transmission, and reduced sensitivity to measurement errors.     

An integrated solid-state solution for secondary electron detection

In this paper, a novel integrated solid-state solution is proposed to replace the vacuum-based photomultiplier tube and other constituent components of the Everhart–Thornley detector, which has been widely used for secondary electron detection in scanning electron microscopy. Compared to the conventional setup, this integrated circuit offers potential merits such as higher cost effectiveness, smaller dimensions, lower voltage and power requirements, and better circuit integration. It was designed and fabricated in an optically-enhanced Austriamicrosystems 0.35 μm CMOS process technology. Results from simulations and experiments have shown that the solid-state detector can operate with a maximum transimpedance gain of 170 dBΩ and minimum bandwidth of 3.6 MHz. It can detect signals with optical power as low as 10 nW while giving a minimum signal-to-noise ratio of 24 dB regardless of gain configuration.     

Characterization of photonic devices by secondary electron potential contrast

Secondary Electron Potential Contrast has been shown recently to be a very effective method for two-dimensional mapping the dopant distribution in Silicon Carbide devices. This work extends the range of applications of the technique to the characterization of photonic devices. Special attention is paid here to the analysis of unipolar and bipolar junctions, heterostructures, and quantum wells.     

扫描电子显微学中二次电子发射过程的蒙特卡洛模拟

利用蒙特卡洛模拟固体中电子散射轨迹的计算方法，系统地研究了扫描电镜中二次电子信号的发射过程。该模拟电子与固体相互作用的蒙特卡洛模型包含了级联二次电子产生的过程，并且采用光学介电函数方法描述电子的能量损失和相伴的二次电子激发。由于模拟计算可以给出背散射电子和二次电子的绝对产额，以及它们随加速电压和样品的原子序数的变化关系，因此可以用于模拟元素衬度和形貌衬度像。还计算得到了关于二次电子产生和发射的其它分布，并与实验结果作了比较。     

Modeling secondary electron images for linewidth measurement by critical dimension scanning electron microscopy

Modeling of critical dimensions scanning electron microscopy with sub-nanometer uncertainty is required to provide a metrics and to avoid yield loss in the processing of advanced CMOS technologies. In this paper, a new approach is proposed, which includes a new Monte Carlo scheme, a new Monte Carlo code, as well as the coupling with electrostatic fields to take into account self-charging effects.     

Mechanism for secondary electron dopant contrast in the SEM

The growing use of secondary electron imaging in the scanning electron microscope (SEM) to map dopant distributions has stimulated an increasing interest in the mechanism that gives rise to so-called dopant contrast. In this paper a range of experimental results are used to demonstrate the wide applicability of the technique. These results are then incorporated into a model where, in particular, the effect of the surface barrier and the vacuum level are considered. It is found that the dominant contribution to the contrast mechanism is due to the three-dimensional variation of the vacuum level outside the semiconductor.