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.     

High-resolution scanning capacitance microscopy by angle bevelling

Scanning capacitance microscopy was performed on bevelled samples to improve the resolution. The dependence of the reverse junction carrier spilling on the bevel angle has been investigated for P and B ion-implanted Si samples. We show an increase of this effect decreasing the bevel angle from 5°44′ to 1°9′. Moreover, the depletion region amplitude measured on the bevelled surface is narrower than on the cross section. We have also studied the spilling dependence on the dopant profile shape and we have found that it increases with the profile slope decreasing in the low concentration region near the junction.     

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.     

Carrier concentration profiles in 6H-SiC by scanning capacitance microscopy

We have used scanning capacitance microscopy to determine two-dimensional carrier distributions in 6H-SiC on both epitaxial layers and implanted samples. Measurements were carried out on cross-sections using metal-covered Si tips. The sample preparation, surface passivation and tip selection have been investigated to obtain an optimised procedure. Implants were performed on p-type 6H-SiC at a substrate temperature of 500°C with N ions at different fluences. The defect profiles were determined by Rutherford backscattering spectrometry. The influence of the implanted damage on the measurements has been investigated by implanted Si-self ions.     

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.     

Determination of doping type by calibrated capacitance scanning microwave microscopy

The investigation of dopant distribution in discrete and highly integrated electronic devices is the main application of Scanning Microwave Microscopy in the semiconductor industry. To reliably determine the dopant type and the relation between differently doped areas within an electronic device, a calibration method based on the estimated complex impedance is introduced. The validation on differently doped silicon demonstrates that the method is able to simultaneously acquire accumulation and depletion capacitances. This enables the calculation of a 2D dopant type profile and furthermore provides a monotonic dependence of the measured capacitance on dopant density.     

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.     

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.     

Evaluation of different oxidation methods for silicon for scanning capacitance microscopy

Different oxides, namely, native, thermal, and wet-chemical (H₂SO₄+H₂O₂ based) oxides on Si are evaluated in the context of scanning capacitance microscopy (SCM). The samples investigated consisted of uniformly doped Si substrates and p-type epitaxial doping-staircase structures with concentrations ranging from 5×10¹⁴ to 2×10¹⁹ cm⁻³. The bias for which the SCM signal (dC/dV) is maximised for the lowest doped region was used for comparing the different oxidation methods. It is shown that for a better evaluation of the surface oxide properties, it is essential to obtain dC/dV curves for a sufficiently large doping range. Best results in terms of low values of flat-band voltages (1 V), uniformity, and consistency across a large doping range were obtained for the wet-chemical oxide. For the native oxide case, the difference in the dC/dV peak bias values obtained at regions doped to 5×10¹⁴ to 10¹⁷ cm⁻³ was anomalously large and suggests appreciable distortion of the dC/dV curves. For the same oxidation procedure the full-width at half-maximum of the dC/dV curve obtained on the cleaved surface is typically 2 times larger than that on the planar (1 0 0) surface. It is most likely that interface states are responsible for the observed distortion.     

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.     

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…     

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.     

表面性质对扫描力显微术成像的影响

利用微接触印刷的方法制备了图形化的自组装膜,考察了膜的表面性质对接触式原子力显微镜（ＡＦＭ）,摩擦力显微镜（ＦＦＭ）和剪切力显微镜（ＳＦＭ）的成像的影响。发现ＡＦＭ能反映样品的表面形貌,而ＦＦＭ和ＳＦＭ的以表面性质的影响较大,在表面性质差别很大的图形表面上会出现图像衬底与表面形貌反转的现象。     

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…