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.     

The application of the scanning electron microscope to the development of high-reliability semiconductor products

Examples are given which illustrate the wide range of applicability of the scanning electron microscope to the processing of high reliability semiconductor products. The three areas selected for presentation are devitrifying solder glass seals for hermetic packages, voltage contrast examination of biased integrated circuits, and metallization corrosion problems encountered in processing technology. The scanning electron microscope gave useful information quickly, and, in some cases, it gave answers that other methods were unable to supply.     

Structural study of an Al73Ni22Fe5 decagonal quasicrystal by high-angle annular dark-field scanning transmission electron microscopy

A water-quenched Al73Ni22Fe5 decagonal quasicrystal was investigated by the selected-area electron diffraction, convergent-beam electron diffraction and high-angle annular dark-field scanning transmission electron microscope methods. The alloy shows very sharp spots and nearly no diffuse scattering in the diffraction patterns, belongs to centrosymmetric space group P10(5)/mmc and is constructed almost by one type of 2 nm diameter atom cluster having mirror symmetry with a highly quasicrystalline order arrangement. Although a small number of 2 nm atom clusters having five-fold symmetry exists, which are similar to those observed in melt-quenched Al70Ni15Fe15, the structure of Al73Ni22Fe5 is considered to basically be the same as that of water-quenched Al72Ni20Co8, which is constructed only by mirror symmetry clusters arranged with a very high quasiperiodicity. The number of valence electrons per atom (e/a) of the present alloy (1.92) is very close to that of Al72Ni20Co8 (1.90), but differs from those of phases constructed by only the five-fold symmetry clusters. This implies that these alloys are Hume-Rothery electron compounds, whose structures are determined primarily by e/a value.     

Measurement of the local latch-up sensitivity by means of computer-controller scanning electron microscopy

The scanning electron microscopy (SEM) technique for the study of the local sensitivity to latch-up of CMOS integrated circuits is discussed. The technique is independent of a particular electric firing mechanism of latchup and does not require in-depth electrical characterization of the IC before the analysis. The electron beam in the SEM is adopted as a localized current injector, and the injected carriers are used to induce the latch-up state rather than to visualize its paths. A minicomputer-based system drives the beam position and automatically blanks the beam if the scan path has to cross areas which should be protected from charge injection. An example of application is described.<>     

Diagnosis in submicron integrated circuits by electric force microscopy

We report device internal voltage contrast measurements on passivated 500 nm wave guides up to 4 GHz. The results were obtained using a new contactless test technique based on a scanning force microscope (SFM). This technique enables voltage contrast even within passivated integrated circuits with nanometer spatial resolution and gigahertz measurement bandwidth. For the first time the high resolution limits of a SFM test system are proofed by device internal signal measurements with both high spatial and temporal resolution.     

Depth profiling of integrated circuits with thermal wave electron microscopy

Nondestructive depth profiling of integrated circuits is performed with thermal wave electron microscopy at 640 kHz modulation frequency.     

Applications of the electron beam exposure system

Successful application of high-speed scanning electron lithography machines such as the electron beam exposure system (EBES) requires the development of suitable materials and processes. We describe how electron resists with improved sensitivity have been used to make high-quality photolithographic master masks in which 1-µm lines and spaces are resolved and also to make MOS integrated circuits with improved packing density and performance.     

Three-dimensional reconstruction by scanning electron microscopy from serial epoxy resin semi-thin sections after ion-etching

Three-dimensional reconstruction was performed using scanning electron micrographs of serial semi-thin sections of Epon embedded specimens. Connective tissue in a rabbit ear chamber was fixed in glutaraldehyde and osmium tetroxide, and then embedded in Epon. One-microm-thick serial sections were cut with a diamond knife, mounted on glass slides and stained with toluidine blue. After observation with a light microscope, the sections were ion-etched with an ion-spatter coater. Following double staining with uranyl acetate and lead citrate, the consecutive sections were ion-coated with platinum. Each serial section was photographed with a scanning electron microscope. Profiles of a blood vessel and fibroblasts were digitized with a computer and computer reconstruction of the blood vessel was performed. Three-dimensional reconstructions showed that the newly formed blood vessel was a cylinder-like, bare endothelial tube with a rather smooth outer surface. Fibroblasts were situated around the endothelial tube. Several openings were found in the endothelial tube, suggesting the morphological feature of high permeability and fragility in newly formed blood vessels. The availability of three-dimensional reconstruction from scanning electron micrographs of serial semi-thin epoxy resin sections was discussed; structures of interest can be reconstructed (1) quickly and easily, (2) without skilful techniques, and (3) almost at the level of ultrastructure.     

Function testing of bipolar ICs and LSIs with the stroboscopic scanning electron microscope

The functional testing of individual circuits is essential for device manufacturers when integrated circuits have not satisfied design specifications. What is required for the functional testing of modern high-density and fast IC and large scale integration (LSI) circuits is a method which has a time resolution in the subnanosecond region and a spatial resolution in the submicrometer region. Furthermore, the test probe must be easy to position on the circuit, and inspection should be possible without having to remove the passivation glass oxide. The authors show that all of these requirements can be satisfied by using a scanning electron microscope (SEM) in the stroboscopic voltage contrast mode. A microcomputer-controlled SEM allows the testing of internal circuit operations with a time resolution of 0.2 ns, a spatial resolution of 0.2 /spl mu/m, and a voltage resolution of 50 mV. Application to a bipolar hex-inverter IC, a quadruple-multiplexer IC, and a 1024 bit PROM in the megahertz region is reported to demonstrate the efficiency of the system.     

Fabrication of integrated circuits using the electron image projection system (ELIPS)

ELIPS is based on the use of an electron image tube principle to project large area (5-cm diameter) ultrahigh resolution (1 micron) electron images from a patterned photocathode onto an electron-sensitive resist layer, thereby replacing the conventional photoresist optical procedures in integrated circuit fabrication [1]. Integrated circuits of minimum linewidths of 0.5 mil have been fabricated to show the practicality of the technique through the full set of mask exposures necessary for a DZTL quad dual input NAND gate. The necessary alignments between successive masks were achieved by an optical dead reckoning technique which allowed the electron image to be adjusted in position and orientation from a known "zero" position to the separately determined location of the pre-existing pattern on the sample. Accuracy of such alignments was ± 2 micron. The much more desirable alignment technique, in which simple devices in the form of alignment marks on the target wafer detect separate electron beams emanating from the cathode, allows rapid alignment to submicron registration and the potential for the complete automation of alignment and exposure. The system provides for the rapid registration and exposure of wafers at high resolution over large areas with great depth of focus under vacuum clean, contactless conditions using an electroresist insensitive to ambient light. It makes practical the fabrication of very high-density planar devices allowing extremely complex large area circuits to be formed. Patterned photocathodes were fabricated by conventional photoresist techniques for the DZTL circuit discussed. For high-resolution (1 micron) patterns, cathodes can be defined in the electron micro-plotter (computer-controlled scanning electron microscope).     

利用场发射扫描电镜的低电压高性能进行材料表征

场发射扫描电子显微镜（FESEM）是一种高分辨扫描电镜,在材料分析中得到广泛应用。尤其是良好的低压高空间分辨性能和低压下良好的SE像相互结合使用,使SEM应用范围得到扩展。     

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.     

电子显微镜平台使用数据分析及管理建议

电子显微镜(以下简称电镜)在生命科学研究中起到了非常重要的作用。随着电镜使用需求的日益扩大,对仪器管理也提出了新的要求。本文利用北京大学生命科学学院仪器中心电镜平台2010年及2017年安装的两台透射电镜的使用数据,详细分析每台电镜的使用时间、使用时长以及相应的用户,并通过描述统计的方法,对这些数据进行分析与整合,包括电镜使用的日内分布、周内分布以及用户群体的变化等。统计得出北京大学生命科学学院电镜平台用户更倾向于在工作时间使用电镜,同时电镜使用的寡头垄断及用户偏好粘性现象明显。建议通过鼓励培训独立用户、合理设计管理者工作时间以及设置设备使用费梯度等方式提高电镜的使用率。     

Efficient Computer-Aided Failure Analysis of Integrated Circuits using Scanning Electron Microscopy

A working, operational system for computer-aided failure analysis of integrated circuits using a scanning electron microscope (SEM) is described. Statistical data analysis and image-processing algorithms are applied to digitized SEM image data. Faults are automatically identified and characterized at the single transistor level. Data-storage requirements for locating and characterizing semiconductor device failures are evaluated. A working, operational method is presented which minimizes these requirements, increases throughput, and permits a high degree of automation.     

Scanning electron microscopy study of the avalanche multiplication factor

A method is presented for examining the distribution of the multiplication process over the active area of shallow junction avalanche diodes using a scanning electron microscope. The multiplication factor is measured as a function of both diode voltage and electron beam energy, and the results are compared with those obtained by more conventional techniques.     

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.     

Nondestructive determination of the depth of planar p-n junctions by scanning electron microscopy

A method was developed for measuring nondestructively the depth of planar p-n junctions in simple devices as well as in integrated-circuit structures with the electron-beam induced current (EBIC) by scanning parallel to the junction in a scanning electron microscope (SEM). The results were found to be in good agreement with those obtained by the commonly used destructive method of lapping at an angle to the junction and staining to reveal the junction.     

A study of diffused bipolar transistors by electron microscopy

Shallow junction bipolar transistors have been fabricated on bulk (001) silicon starting material using a diffusion processing technology. The resultant junction depths were about 0.5 and 0.8 μ m respectively for the emitter-base and base-collector junctions. The crystallographic defects present have been detected and characterized using a combination of electrical measurements, the electron beam induced current (EBIC) mode of the scanning electron microscope (SEM) and both conventional and high voltage transmission electron microscopy (TEM).Two types of dislocations were identified in the TEM. The first consisted of an orthogonal array of sessile, diffusion-induced edge dislocations located about halfway down in the heavily doped emitter. The second type consisted of 60° glissile dislocations that looped down from the orthogonal array and in some cases penetrated the emitter-base junction.Observations of a number of 60° dislocations yielded a good correlation between their depth and their contrast when imaged in the EBIC mode of the SEM. The 60° dislocations locally retard the emitter diffusion when they lie near to the emitter-base junction. Local breakdown effects under reverse bias were observed at the sites of these dislocations.     

Stabilized emission from micro-field emitter for electron microscopy

Micro-fabricated field emitter for the application in miniaturized scanning electron microscope (MSEM) was fabricated on silicon substrate. Field emission studies of the micro-fabricated field emitter were carried out in an ultra high vacuum system. A simple voltage controlled feedback circuit was designed and used to regulate the gate voltage in order to improve the emission current stability of the micro-fabricated field emitter. Preliminary results showed that the emission current fluctuation ((I_max − I_min)/I_ave) was reduced from 80% without feedback current stabilizer to less than 1% with the circuit control.     

Quantitative measurement with high time resolution of internal waveforms on MOS RAMs using a modified scanning electron microscope

The growing packing density of integrated circuits calls, to an increasing extent, for the testing of the functioning of the individual circuits of ICs. If a mechanical prober is used for this purpose, the resulting capacitive loading of the circuit is liable to alter its performance. It is shown in the present work that the electron beam represents an ideal nonloading and nondestructive probe which can be finely focused and positioned on measuring points within the circuit under test. A modified scanning electron microscope allows the recording of waveforms within a circuit with a voltage resolution of the order of 10-100 mV and a time resolution of less than 1 ns. The efficiency of the technique was demonstrated by measuring the internally derived clock pulses and the voltage distributions of a digit-line of a 4096-bit MOS RAM and comparing the results with computer simulations.