Quantitative scanning capacitance microscopy analysis of two-dimensional dopant concentrations at nanoscale dimensions

We have applied the scanning capacitance microscopy (SCM) technique of twodimensional (2-D) semiconductor dopant profiling to implanted silicon cross sections. This has permitted the first direct comparison of SCM profiling scans to secondary ion mass spectroscopy (SIMS) depth profiles. The results compare favorably in depth and several readily identifiable features of the SIMS profiles such as peak concentration and junction depth are apparent in the SCM scans at corresponding depths. The application of dopant profiling to two dimensions is possible by calibrating the SCM levels with the one-dimensional (1-D) SIMS data. Furthermore, we have subsequently simulated the SCM results with an analytic expression readily derivable from 1-D capacitance vs voltage capacitance-voltage theory. This result represents a significant breakthrough in the quantitative measurement of 2-D doping profiles.     

Static capacitance contrast of LSI covered with an insulator film in low accelerating voltage scanning electron microscope

A new image contrast is reported for LSIs covered with an insulator film in a low accelerating voltage scanning electron microscope. The surface region above the conducting lines is often observed brighter than that without conducting lines. This contrast is quasi-stationarily observed contrary to well-known capacitive-coupled voltage contrast, and is called static capacitance contrast. The optimum irradiation conditions for the maximum image contrast is studied and its mechanism is discussed.     

Use of scanning capacitance microscopy for controlling wafer processing

Scanning capacitance microscopy and electrostatic force microscopy have been used to characterize commercial semiconductor devices at various stages of the fabrication process. These methods, combined with conventional atomic force microscopy, allow to visualize qualitatively the oxide thickness, the nature of dopants and the exact position of implanted areas.     

Scanning electron mirror microscopy and scanning electron microscopy of integrated circuits

The recently developed scanning electron mirror microscope (SEMM) is compared with other types of electron microscopes, such as the electron mirror microscope (EMM) and the scanning electron microscope (SEM), for examining integrated circuits. Potential advantages of the SEMM include high resolution, elimination of electron bombardment damage, and high sensitivity of voltage gradients, magnetic fields, and topography. Preliminary observations of integrated, circuits obtained with the feasibility SEMM at various specimen potentials are discussed.     

Experimental investigation of the dielectric-semiconductor interface with scanning capacitance microscopy

An experimental investigation of how interface states effect scanning capacitance microscopy (SCM) measurements is presented. Different sample polishing procedures were used to make SCM samples that would have different interface state densities, but identical oxide thicknesses. By comparing SCM signals of these samples, the effect of interface states could be singled out. The interface states of these SCM samples were found to have an amphoteric energy distribution. The magnitude of the maximum SCM signals (maximum dC/dV in dC/dV versus dc bias, V_dc, plots) is independent of the interface-trapped charges, while the full width at half maximum (FWHM) of the dC/dV–V_dc curves is broadened with the interface states. The physics of SCM interface states effect is also discussed.     

Progress in aberration-corrected scanning transmission electron microscopy

A new corrector of spherical aberration (C(S)) for a dedicated scanning transmission electron microscope (STEM) is described and its results are presented. The corrector uses strong octupoles and increases C(C) by only 0.2 mm relative to the uncorrected microscope. Its overall stability is greatly improved compared to our previous design. It has achieved a point-to-point resolution of 1.23 A in high-angle annular dark field images at 100 kV. It has also increased the current available in a 1.3 A-sized probe by about a factor of ten compared to existing STEMs. Its operation is greatly assisted by newly developed autotuning software which measures all the aberration coefficients up to fifth order in less than one minute. We conclude by discussing the present limits of aberration-corrected STEM, and likely future developments.     

Evaluation of scanning capacitance microscopy sample preparation by focused ion beam

Due to the continuous reduction of the critical dimensions of semiconductor devices, it becomes very important to know the two dimensional (2D) doping profile for electrical performance of devices. Scanning Capacitance Microscopy (SCM) is a powerful technique for qualitative analysis of 2D doping species distribution, measuring small capacitance variations with high spatial resolution. For 2D carrier profiling, the region of interest must be accessible to the profiling instrument. SCM samples require cross-sectioning to expose the inner sample at a visible surface. In some analysis, the failure is localized at a very accurate address up to hundreds of nanometers. With the traditional polishing method of sample preparation it is very difficult to reach the exact location. For this reason we are investigating a new way to prepare SCM sample with Focused Ion Beam (FIB) and plasma etch in order to accurately choose the scanning zone. This paper presents a method to obtain SCM scans after a sample preparation by FIB and the influence of the FIB and the Plasma etcher on cross-sectioned SCM samples.     

铜锌合金锥套的扫描电镜失效分析

铁路电气化工程用的接触线端锚固线夹锥套 ,系采用Ｈ6 2黄铜制造 ,用于导电铜接触线的锚固。在使用过程中发生开裂破损 ,导致铜导线脱落。本文采用扫描电子显微镜、Ｘ射线能谱仪、金相显微镜等设备对其进行了全面的失效分析 ,通过对其断口特征的分析 ,加工工艺分析、受力分析 ,找出了该夹锥套的断裂原因。实验通过扫描电镜和Ｘ射线能谱仪 ,对断口进行了成分分析。在断口上发现大量的Ｓ ,少量的Ｃｌ等腐蚀性元素。同时还在断口上发现有Ｍｇ ,Ａｌ,Ｓｉ,Ｋ ,Ｃａ,Ｔｉ,Ｆｅ等非基体元素。从断口形貌上可以看到 ,试样的断口呈脆性断裂的颗粒状…     

Correlative light microscopy, scanning electron microscopy, and transmission electron microscopy of osmium-macerated biological tissues

A method facilitating correlation of light microscopic (LM), scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images was developed. Rat kidney and heart were initially subjected to the osmium maceration procedure and then embedded in acrylic resin. Semithin sections of the tissue blocks were first provided for LM and then examined by SEM after resin removal. Furthermore, the ultrathin sections adjacent to the semithin sections were observed by TEM. The three-dimensional images of intracellular organelles provided an informative adjunct to LM and TEM.     

Displacement current sensor for contact and intermittent contact scanning capacitance microscopy

In this study a displacement current capacitance sensor (DCCS) for scanning capacitance microscopy (SCM) is introduced. It can be used for both intermittent contact (IC) and contact-SCM operation. Based on I/V conversion and subsequent lock-in amplification a displacement current can be detected and used as a measure for dopant concentration. Therefore a periodic variation of the AFM tip substrate capacitance is required. This can be achieved either by a periodic tip oscillation (IC-SCM) or an applied AC voltage between tip and sample (contact-SCM). The advantage of the DCCS is the linearity, which makes it possible to detect absolute dopant concentrations.     

模拟扫描电镜像衬度的体构件Monte Carlo方法

利用Mollte Carlo计算方法可以模拟电子束与样品的相互作用过程,从而了解扫描电子显微学中信号的产生机制,本工作中,我们采用体构件法来产生复杂试样的几何构型,利用光线追踪算法求得散射事件间的步长抽样修正。电子散射的物理模型则采用Mott散射截面描述电子与原子间的弹性相互作用,以及用介电函数理论描述电子与固体的非弹性相互作用,同时还考虑到了二次电子的级联产生过程．以此,我们模拟计算出了若干复杂几何体的二次电子像和背散射电子像。     

神经干细胞克隆内细胞的扫描电镜超微结构研究

近年来,随着神经干细胞体外培养模型的建立,神经干细胞的研究正逐渐成为生命科学领域新的研究热点。为了观察神经干细胞克隆在分化过程中超微结构的变化以及细胞间的相互关系,我们做了单一神经干细胞克隆在poly-orithine上发生分化迁移过程中的扫描电镜观察。     

雀石蕊地衣体形态的扫描电镜研究

地衣是菌、藻共生的生物复合体 ,它既不同于一般真菌 ,又有别于一般藻类 ,是新的形态学与生物学实体 ,它们的共生关系是迄今为止任何互惠共生现象中最突出、最完善的类型。对其形态学方面的研究 ,有利于人们对生物共生现象进一步的了解 ,更深入的揭示其本质。地衣在我国分布广泛 ,蕴藏极为丰富。由于地衣对大气污染十分敏感 ,因此 ,人们常把地衣作为监测大气污染的灵敏指示植物加以利用 ;地衣中含有大量的防腐成分如 :松萝酸、地衣硬酸等 ,它们均具有很高的抗菌活性。以往人们对地衣形态学方面的研究 ,大都是限于一般的形态结构水平 ,本文利…     

环扫电镜表征影响因素及芯片失效分析应用

对环境扫描电镜(ESEM)表征影响因素进行试验研究,根据半导体芯片的结构,进行成像参数优化,试验结果表明较为适合的优化参数为:腔室气压40Pa~80Pa,加速电压10kV~20kV.研究了裙散效应对能谱分析的影响,结果表明非分析区域元素含量与离能谱分析点的距离呈幂函数衰减,应证了文献报道的理论计算,对于能谱分析排除干扰元素有一定的参考意义.针对破坏性物理分析(DPA)试验中发现的塑封器件腐蚀缺陷,利用ESEM在优化参数下进行机理分析,结果表明玻璃钝化层裂纹是导致铝金属条被腐蚀的原因,而玻璃钝化层裂纹是由于器件材料性质不匹配,在热载荷条件下产生热应力而引起.这种表层缺陷极有可能因为镀膜而被掩盖,因此,利用ESEM检测半导体器件具有一定的必要性.     

Histochemistry of food tissue by colour scanning electron microscopy

A low-vacuum scanning electron microscope (SEM) allows microscopy of insulating specimens without metal coating, and so preserves the intact colour information on the specimen surface. We have attempted a new approach to characterize constituent distribution of food tissues by a histochemical method utilizing a colour SEM with an optical microscope and the low-vacuum SEM through digital image processing. To observe food tissues such as brown rice and adzuki bean, a colour SEM image of the specimen that has been stained by a modified method used in optical microscope histochemistry has proved to provide information of both the microscopic structure and constituent distribution on the specimen surface.     

基于扫描电子显微镜的半导体掺杂剂含量剖面分析研究进展

掺杂剂浓度剖面分析是半导体器件研发、诊断和电学性能提升的关键.扫描电子显微镜因具有埃级空间分辨率、成像速度快、荷电效应弱和辐照损伤小等优点,在表征掺杂半导体方面独具优势.本文简要介绍了扫描电子显微镜在掺杂半导体表征方面的研究进展及挑战,包括SEM图像中掺杂衬度的产生机理、成像参数以及SE的能量和出射角度对掺杂衬度的影响...     

Local electronic properties of AlGaN/GaN heterostructures probed by scanning capacitance microscopy

Local electronic properties in Al_xGa_1−xN/GaN heterostructure field-effect transistor epitaxial layer structures are probed using scanning capacitance microscopy. Acquisition of scanning capacitance images over a wide range of bias voltages combined with theoretical analysis and numerical simulation allows the presence, detailed nature, and possible structural origins of nanometer- to micronscale inhomogeneities in electronic structure to be elucidated. Substantial lateral variations in local threshold voltages for transistor channel formation are observed, at length scales ranging from submicron to >2 μm, and found to arise primarily from local variations in Al_xGa_1−xN layer thickness. Features in electronic structure are also observed that are consistent with the existence of networks of negatively charged threading edge dislocations, as might be formed at island coalescence boundaries during epitaxial growth. The negative charge associated with these structures appears to lead to local depletion of carriers from the channel in the Al_xGa_1−xN/GaN transistor epitaxial layer structure.     

Influence of interface traps and surface mobility degradation on scanning capacitance microscopy measurement

Although scanning capacitance microscopy (SCM) is based on the MOS capacitance theory, the measurement frequency is 915-MHz instead of 100 kHz to 1 MHz in conventional MOS capacitance-voltage measurement. At this high frequency, the reactance of the probe tip-to-substrate capacitance can become smaller than the series resistance of the substrate inversion layer, particularly when the surface mobility is degraded. The response of the oxide-silicon interface traps to SCM measurement is also different due to the use of a 10-kHz signal to determine dC/dV. In this paper, we compare experimental and simulation data to demonstrate the effects of interface traps and surface mobility degradation on SCM measurement. Implications on the treatment of SCM data for accurate dopant profile extraction are also presented.     

水生植物冷冻扫描电镜和常规扫描电镜成像效果比较

比较了三种水生植物(单星藻、芜萍和水蓑衣)的冷冻扫描电镜和常规扫描电镜成像效果,两种方法观察到的样品表面结构差异明显.冷冻扫描电镜下的样品形态饱满、无塌陷皱缩,藻细胞表面的脊状凸起和水生植物叶片上的气孔结构清晰、无变形;而常规扫描电镜冷冻干燥的样品因脱水皱缩变形,甚至表面部分塌陷.冷冻扫描电镜可以有效地解决水生植物样品因脱水而皱缩变形的问题,最大程度地保持样品原本的细微结构特征,非常适合用于含水量高的水生植物样品的超微结构观察.     

肿瘤细胞侵袭性体外检测的扫描电镜观察

肿瘤细胞的侵袭性是确定肿瘤恶性程度的指标之一 ,胎盘羊膜半透明 ,结构简单 ,可用作癌细胞培养的支持物 ,并可观察其向基质浸润程度 ,本文目的是用扫描电镜观察羊膜结构及癌细胞在羊膜侵袭的形态改变。材料与方法新鲜足月胎盘 ,剥离胎儿面羊膜 ,洗净 ,剪成 2 cm直径的圆片 ,放入 2 4孔培养板 ,培养 2 4h,加入食管癌细胞析 SHEEC1细胞[1] 。第 2天起 ,每天取 4孔羊膜检查 ,共 6天。羊膜在 2 .5 %戊二醛固定 ,常规脱水 ,置换 ,真空喷涂 ,在日立 H30 0电镜扫描配件下观察。结果在扫描电镜下 ,羊膜表面为一层上皮细胞铺盖 ,上皮细胞大小一致…